Counteracting the Harms of Microplastics on Humans: An Overview from the Perspective of Exposure

Abstract

Microplastics are pervasive environmental pollutants that pose risks to human health through ingestion and inhalation. This review synthesizes current practices to reduce exposure and toxicity by examining major exposure routes and dietary interventions. More than 130 papers were analyzed to achieve this aim. The findings show that microplastics contaminate a wide range of food products, with particular concern over seafood, drinking water, plastic-packaged foods, paper cups, and tea filter bags. Inhalation exposure is mainly linked to indoor air quality and smoking, while dermal contact poses minimal risk, though the release of additives from plastics onto the skin remains an area of concern. Recommended strategies to reduce dietary exposure include consuming only muscle parts of seafood, moderating intake of high-risk items like anchovies and mollusks, limiting canned seafood liquids, and purging mussels in clean water before consumption. Avoiding plastic containers, especially for hot food or microwaving, using wooden cutting boards, paper tea bags, and opting for tap or filtered water over bottled water are also advised. To mitigate inhalation exposure, the use of air filters with HyperHEPA systems, improved ventilation, regular vacuuming, and the reduction of smoking are recommended. While antioxidant supplementation shows potential in reducing microplastic toxicity, further research is needed to confirm its effectiveness. This review provides practical, evidence-based recommendations for minimizing daily microplastic exposure.

1. Introduction

In the past ten years, the pollution caused by microplastics has emerged as a significant global concern, potentially impacting ecosystems, biodiversity, and human health [1]. The ongoing presence of these contaminants in ecological systems has also been acknowledged as an urgent worldwide challenge [2]. This era has been termed the “Plasticene,” a new phase in history characterized by vast amounts of microplastic accumulation [3]. The widespread issue of plastic pollution is recognized as a risk to both the environment and the health of humans and animals, partly due to the presence of chemicals in plastics [4]. Chemicals in plastics are released into the environment over time, causing harm to the ecosystem. Additionally, plastics can undergo degradation in the environment due to mechanical, biological, and chemical actions that generate microplastics [5,6].

Microplastics are usually described as plastic fragments measuring under 5 mm in size. Secondary microplastics are produced from the breakdown of larger plastic debris, whereas primary microplastics are intentionally created for specific purposes, such as microbeads found in personal care and cosmetic products [7]. Microplastics can also be classified by their shapes, which include categories such as pellets, fragments, fibers, films, beads, and sponges or foams [8]. Certain shapes of microplastics are more common in particular environments because of human activities and natural sorting processes. For example, fibrous microplastics often outnumber other shapes like fragments and granules because they originate primarily from synthetic textiles and are shed during washing and wear [9]. Fibrous microplastics are also common in the marine environment due to the use of fishing nets and ropes [10]. Additionally, microplastic fibers tend to stay in the water column longer than other shapes due to their high surface-area-to-volume ratio and low density. Because fibers are long and thin, they experience more drag in water, slowing their sinking rates [11].

The widespread presence of microplastics results in their entry into living organisms. In the marine environment, microplastics have commonly been detected in filter feeders and fish [12,13]. Dowarah et al. indicated that the count of microplastics found in the bivalves Perna viridis and Meretrix meretrix varied between 0.50 ± 0.11 and 4.80 ± 1.39 per individual, which was influenced by their capture locations. Additionally, the proportion of particles measuring less than 100 μm was 61.02% in M. meretrix and 77.42% in P. viridis [14]. Lo et al. investigated the presence and quantity of microplastics in marine fish sampled from the waters of Hong Kong. They discovered that more than half (57.1%) of the fish showed microplastic presence in their digestive systems, with the total microplastic counts varying from none detected to as many as 44 items per fish [15]. Microplastics have also been found in freshwater fish. In a study by Yin et al., it was found that the quantity of microplastics present in the digestive tracts of 11 different fish species from Lake Chao, China, ranged between 2.85 and 8.38 microplastic items per individual [16]. Additionally, the number of microplastics observed in the gills also varied, with counts from 3.06 to 8.90 items per individual. The researchers noted a predominant presence of fibrous microplastics, particularly those that were small in size (less than 1 mm) and made of polypropylene [16].

Studies have unveiled the presence of microplastics in various terrestrial organisms comprising soil-dwelling invertebrates, insects, livestock, amphibians, rodents, and birds [17,18]. Mackenzie and Vladimirova analyzed the stomach contents of 311 individuals across three bird species in Paraguay and discovered microplastics to be present in all 81 species examined [19]. Wu et al. examined the presence of microplastics across 19 farms raising various livestock and poultry. They found a significant presence of microplastics in livestock manure, with quantities between 667 and 990 items per kilogram of wet weight. Additionally, the microplastics found in feed samples from the farms varied from 36 to 139 items per kilogram of wet weight [20]. This indicates the potential contamination of livestock by microplastics. The detection of microplastics in a wide array of aquatic and terrestrial organisms implies that they have very likely entered the food chain, leading to human exposure to microplastics. Studies have revealed that microplastics are found in human bodies, including in the placenta (12 fragments in four placentas) [21], lung tissues (33 particles and four fibers in 13 tissue samples) [22], and blood (1.84–4.65 μg/mL) [23]. There are also multiple reviews dedicated to human exposure to microplastics [24,25,26].

The exposure and entry of microplastics into human bodies spark concerns about their potential toxicity, which has led to numerous research and review articles in the genre being published [6,27,28]. For instance, generally, based on cell line and in vivo studies on mice and rats, microplastics have been found to have varying levels of toxicity to the digestive system, respiratory system, cardiovascular system, nervous system, reproductive system, immune system, and endocrine system [6,27]. While the impacts of human exposure to microplastics have received much attention, there are few reviews that focus on the reduction of microplastic exposure and toxicity in humans. This review aims to synthesize practices that could reduce exposure to and toxicity from microplastics by examining the main human exposure routes to microplastics and dietary interventions that could reduce their toxic effects. In doing so, it hopes to provide practical perspectives that can contribute to counteracting the harms caused by microplastics to humans.

2. Review Methodology

This narrative review was conducted through a systematic search of reputable scientific databases, including Web of Science, Scopus, and ScienceDirect. The search strategy involved keyword combinations related to microplastics, human exposure, toxicity, mitigation, and intervention strategies, utilizing Boolean operators (AND/OR) for optimization. Examples of search queries included: (1) “microplastics” AND “human” and (“toxicity” OR “health effects” OR “biological impact”), (2) “microplastics” AND “human exposure” AND “mitigation”, and (3) “microplastics” AND “detoxification” AND “preventive measures”. The selection criteria required that articles be peer-reviewed, published in English, and primarily from the last decade, with preference given to studies published in the last five years. Additionally, selected studies needed to address the occurrences and abundances of microplastics in major human exposure pathways. The selected articles also included those that describe the interventions aimed at reducing human exposure to microplastics, as well as both in vivo and in vitro studies demonstrating measures to reduce microplastic toxicity upon exposure. Articles that exclusively focus on microplastic–environment interactions or general ecotoxicity without direct relevance to human health were excluded from the review. Articles that discuss the general toxicity without addressing the measures or intervention strategies that could help to reduce microplastic exposure and toxicity were also excluded.

3. Human Exposure to Microplastics

Before discussing measures to reduce exposure, it is essential to illustrate how humans are exposed to microplastics. The main exposure routes include ingestion, inhalation, and dermal contact.

The pervasive presence of microplastics in the environment has led to their infiltration into the human body via the food chain. Research has indicated that microplastics can be found within the tissues and organs of aquatic species [29,30]. Because of their small dimensions, microplastics absorbed by marine life can transfer to humans, either directly or indirectly, via dietary pathways [31]. Recent studies on microplastic presence in food have increasingly targeted seafood and drinking water. Seafood ranks among the food categories most affected by microplastics. Research indicates that marine organisms ingest microplastics, which are ultimately consumed by humans. The quantity of microplastics ingested by seafood varies significantly, with bivalves averaging from 0 to 10.5 items per gram, and fish ranging from 0 to 20 items per individual [32]. Consequently, seafood receives greater emphasis in this review to offer actionable suggestions for minimizing human exposure to microplastics through consumption. Furthermore, microplastics have been detected in consumable goods like salt, honey, sugar, and sardines [33]. Studies show that the contamination of microplastics is more common in organisms at lower trophic levels [34]. Additionally, humans can ingest microplastics from drinking water, particularly from contaminated water sources [35]. Microplastics are commonly found in freshwater bodies and drinking water, with their concentrations varying widely across samples, ranging from 0.01 to 100 million particles per cubic meter [36]. The packaging of drinking water may influence its microplastic levels. According to estimates from Cox et al., individuals who drink bottled water could ingest around 90,000 microplastics each year, while those who consume only tap water would take in about 4000 microplastics annually [37]. This indicates higher microplastic content in bottled water. Additionally, they projected that the yearly intake of microplastics through food could range between 39,000 and 52,000 per person, varying based on age and gender [37]. Research conducted by Catarino et al. highlighted that the consumption of fibers from indoor dust settling on plates during meals was greater than the ingestion of microplastics from eating mussels, suggesting that a significant amount of microplastics might be ingested through dust fallout at home [38].

Microplastics have been found in the atmosphere across the globe, including remote areas [39,40,41], indicating that these particles are widespread and pose potential health risks through inhalation. Amato-Lourenço et al. detected residues of microplastics in lung tissue samples from adults who do not smoke [22]. Jenner et al. reported the presence of microplastics in all areas of the lungs, predominantly microplastic fragments and fibers [42]. A research study involving European participants found that bronchoalveolar lavage fluid contained microplastics, averaging 9.18 particles for every 100 mL, with an average diameter of 1.73 mm [43]. Alarmingly, inhaled microplastics have been found to migrate to placental and fetal tissues [44]. Microplastics can travel through the air, impacting even remote and sparsely populated areas [45]. A study analyzing airborne fiber particles in Beijing indicated that microplastics comprised 34.6% of the sample [46]. Notably, trace levels of airborne microplastics were detected even after implementing strict measures aimed at their removal [47]. In a study conducted utilizing a thermal breathing model of the human body, it was found that a typical male adult who engaged in light physical activities inhaled as many as 272 microplastics each day from indoor air [48]. Infants and toddlers were observed to inhale 3 to 50 times more microplastics than adults [49].

Contact with microplastics through the skin may not be the most critical exposure pathway, even though nanoscale particles can penetrate human skin. However, the potential harmful effects, particularly of smaller nanoplastics (under 100 nm), should not be overlooked. The skin’s outer layer, known as the cuticle, acts as the body’s primary defense, functioning as a barrier that limits the entry of most substances, including particles and chemicals. While this dermal barrier is effective in many instances, it does have its limitations. Key factors that affect the ability of plastic particles to permeate the skin include their size and chemical properties. Particles that are smaller than 100 nm and exhibit more reactive surfaces are more likely to penetrate the skin [50]. Additionally, larger particles can sometimes get through hair follicles, sweat glands, or areas of broken skin [51]. A study revealed that nanoparticles from cosmetics can cause harmful effects on skin cells (keratinocytes), leading to oxidative stress, inhibited cell growth, and aging effects [52].

4. Reducing Exposure to Microplastics

4.1. Reducing Exposure Through Ingestion

4.1.1. Seafood

Exposure to microplastics can be reduced by ingesting food or food parts containing lower microplastic content. Microplastics tend to accumulate in the digestive systems of fish, and since this part is typically not eaten by humans, it reduces the risk of human exposure to microplastics through fish consumption [53,54]. A study focused on commercially significant fish species and a crustacean in the Musa estuary, and one location in the Persian Gulf discovered a total of 828 microplastics present in the gills, gastrointestinal tracts, liver, muscle, and skin of various demersal and pelagic fish, including Cynoglossus abbreviatus, Platycephalus indicus, Saurida tumbil, and Sillago sihama across all five locations [55]. Furthermore, microplastics were detected in the exoskeleton and muscle tissues of tiger prawn, Penaeus semisulcatus (green tiger prawn), at three of these sites, indicating that microplastics have permeated the muscle tissues of seafood. Microplastic counts in the muscles of the seafood ranged from 7 to 21 pieces (5 to 22% of the total) [55]. The presence of microplastics was confirmed in the gastrointestinal tract, gills, and exoskeleton of Litopenaeus vannamei (white leg shrimp) raised in a commercial aquaculture facility. The research indicated that the microplastic content in the shrimp’s exoskeleton and gastrointestinal tracts was consistently greater per gram of tissue throughout all growth stages. After seven months of cultivation, a total of 1211 microplastics were found across the three tissues, with percentages of 25.3 in the gastrointestinal tracts, 32.7 in the gills, and 42.0 on the exoskeleton. When comparing microplastic abundance per gram of tissue, the gastrointestinal tract (193.0 ± 76.6 MPs/g) showed significantly higher levels than the exoskeleton and gills [56]. The exoskeletons of L. vannamei and Penaeus monodon (black tiger shrimp) were found to contain microplastic particles. The mean concentrations of microplastics found in the bodies of the two shrimp species were recorded as 4.99 particles per gram and 1.87 particles per gram, respectively [57]. By removing non-muscle parts and consuming only the muscles, the exposure to microplastics can be significantly reduced (Figure 1). Another study supports this finding, showing that microplastics are most prevalent in the gastrointestinal tract (40.0%) of two types of commercial marine fish, specifically Mullus barbatus and Alosa immaculata [58]. In contrast, brain tissues showed the lowest concentration of microplastics at 7.0%. This could be due to the effect of the blood–brain barrier, which prevents the entry of large microplastics into the brain [59]. After the gastrointestinal tract, the gills showed the second-highest concentration of microplastics, followed by the muscles [58]. Since the gastrointestinal tract and gills of fresh fish are not typically consumed, the risk of microplastic transfer to humans through the ingestion of these parts is generally low.

Crustaceans, which feed by filtering water, present a higher risk because people often consume their entire digestive systems. Saborowski et al. found that the Atlantic ditch shrimp, Palaemon varians, easily consumed fluorescent polystyrene microbeads ranging from 0.1 to 9.9 µm in size experimentally [60]. The food particles and microbeads that are ingested accumulate in the stomach, where they are broken down and mixed with digestive enzymes. Within the stomach, there is a filtering system that sorts the ingested particles by size. Liquids and the smallest particles (0.1 µm) can pass through this filter and move into the midgut gland, where nutrient absorption occurs, along with the production and release of digestive enzymes. Most of the large particles, along with many smaller ones, are expelled from the body through the hindgut in the feces [60]. Reunura and Prommi discovered that the gastrointestinal tracts of female and male freshwater prawns contained an average of 33.2 and 33.4 per individual, respectively, while the white leg shrimps contained 33.31 ± 11.00 per individual, with their respective levels of microplastic per gram of gut material recorded as 32.7, 32.1, and 10.3 items [61]. The detection of microplastics in the gut of commercial shrimps was also reported in other studies [62,63,64]. This highlights that removing the gastrointestinal tracts of shrimps when consuming them could significantly reduce the exposure to microplastics. Removing their exoskeletons further reduces such exposure (Figure 1). Currently, there are limited studies comparing the microplastic distribution in different body parts of commercial aquatic organisms upon the ingestion of microplastics.

It is evident that different crustacean and fish species have different levels of microplastics in their body, which also vary depending on the places where they are caught. For instance, a recent study indicated that Portunus plagicus (a crab species) muscle tissue collected from the Persian Gulf exhibited the highest amount of microplastics, measuring 1.04 items per gram [65]. This was followed by P. semisulcatus (green tiger prawn), Metapenaeus affinis (Jinga shrimp), Tenualosa ilisha (Hilsa shad), and Platycephalus indicus (Bartail flathead) at 0.62 items/g, 0.45 items/g, 0.33 items/g, and 0.11 items/g, respectively. Generally, the gathered crustaceans were noted to contain larger quantities of microplastic particles. Crabs harvested downstream of the Bahmanshir River had the highest prevalence of ingested microplastics, constituting 41.0% of the total particles [65]. The ingested microplastics occurred in 24.0% of P. semisulcatus, 18.0% of M. affinis, 13.0% of T. ilisha, and 4.0% of P. indicus, implying higher occurrence rates and abundance of microplastics in crustaceans [65]. The consumption rate of microplastics by P. semisulcatus (0.62 items/g) corresponds closely to the findings of Devriese et al., which reported a rate of 0.68 items/g in the coastal areas of the Southern North Sea [66]. However, Abbasi et al. (2018) did not report a notably higher level of microplastics in green tiger prawns compared to fish [55]. The microplastics in seafood items vary by the locations where they are caught, making it challenging to control the sources of seafood entering the market. These items may come from different areas, each with distinct levels of microplastic pollution, which can change over time. Additionally, studies indicate that crabs may contain similar or even higher levels of microplastics in their tissues compared to shrimps and fish. This observation is supported by research that found microplastics (sized 1 to 5000 µm) in crabs and fish sampled from a mangrove wetland in China, with amounts varying between 1.224 and 7.790 items per individual in crabs and 1.779 and 8.610 items per individual in fish [67]. A study conducted by Ogunola et al. (2022) examined crustacean samples obtained from seafood markets and coastal areas in Australia. The findings revealed that 48% of the crustaceans were found to have microplastics present [68]. Specifically, prawns had an average of 0.8 ± 0.1 items per individual, while crabs exhibited an average of 1.6 ± 0.1 items each [68]. Thus, crabs may be a major contributor to microplastics in seafood, and reducing their consumption could decrease exposure to microplastics from seafood intake.

At present, there is a scarcity of research linking environmental microplastic levels to those found in commonly consumed aquatic organisms, especially mobile species, as their movements and migrations complicate such investigations. For sedentary organisms, particularly mussels, Qu et al. studied the microplastic levels in both water and mussels (Mytilus edulis, Perna viridis) across 25 locations along the coast of China, revealing a notable positive correlation between the concentrations of microplastics found in the water and those present in the mussels [69]. The study by Scott et al. (2019) indicates that, while the abundance of microplastics in mussels is linked to the microplastics present in the sediment around them, it does not show a correlation with either the concentration of microplastics at the sea surface or the size of the mussels themselves in their studied locations [70]. Both studies highlight that the microplastic abundance in mussels is closely related to their surroundings.

Mussels, along with various types of mollusks, as well as anchovies, are significant contributors to microplastic exposure. Commercial bivalve mollusks have the capability to filter and accumulate microplastics of varied sizes, depending on the concentration and distribution of plastic particles in the seawater. Microplastics measuring between 2 and 10 μm are subsequently absorbed from the digestive system into the circulatory system, where they are stored for extended periods. Research has noted the presence of 3 to 5 fibers per 10 g of various mussel species (M. edulis and M. galloprovincialis) in Belgium [71]. In Chinese commercial bivalves, the range of detected microplastics varied from 2 to 11 particles per gram (5–5000 μm) and 4 to 57 pieces per bivalve [1,72]. No major differences in the microplastic levels were observed between wild and farmed mussels [73,74]. The use of a depuration treatment can facilitate the removal of some of the larger ingested microplastics from mussels and oysters, thus implying that keeping harvested mussels in clean water for a period of time could reduce the microplastics in them (Figure 1) [74]. Regarding anchovies, a study of five dried anchovy products sourced from the Western Gulf of Thailand revealed that the levels of microplastics in these dried anchovies ranged from 0.47 to 3.18 particles per gram. The microplastics identified were between 109 and 1006 µm in size [75]. Hasan et al. confirmed the higher abundance of microplastics in dried ribbon fish (Trichiurus lepturus), with 46 particles per gram compared to the fresh fish (6.41 particles/g in the gills, 6.20 particles/g in the gastrointestinal tract, and 1.2 particles/g in the muscles) [76]. Dried hairfin anchovies also contained more microplastics (2.17 particles/g) than the fresh ones (0.06 particles/g) [76]. This points to relatively lower microplastics in fresh fish muscles, and the moderate consumption of mollusks and dried fish could lower microplastic exposure. As anchovies are typically consumed whole, microplastics present in the non-muscle parts of the fish may be ingested by humans.

Among the 20 canned sardines and sprats examined by Karami et al., 16 brands showed no sign of plastic particles, while the remaining four brands contained between 1 and 3 particles each. The detection of micro- and mesoplastics in canned sardines and sprats may result from these particles migrating into the edible sections, poor gutting practices, or potential contamination during the canning process [77]. The authors assessed the potential health risks related to their consumption, deeming it minimal because of the low occurrence of micro- and mesoplastics larger than 149 μm, along with the lack of dangerous inorganic substances [77]. Akhbarizadeh et al. identified 128 microplastics within 50 samples of canned tuna. The lowest concentration of microplastics was found in yellowfin tuna packed in soybean oil, averaging 0.05 items per gram of muscle, while the highest concentration was observed in longtail tuna preserved in brine, with an average of 0.22 items per gram of muscle [78]. Furthermore, 80% of the samples analyzed contained at least one microplastic. However, the detected levels were similar to those found in fresh fish muscles and were lower than the quantities reported in crustaceans, mollusks, and dried fish [78]. Variability in microplastic content exists between canned fish produced in different regions. For instance, an analysis of four brands of tuna soaked in water and oil sold in Ecuador revealed a notable microplastic concentration of 6.9 items per gram in tuna canned in water and 4.4 items per gram in tuna canned in oil [79]. However, more studies indicate that levels of microplastics in canned fish are comparable to those found in fresh fish muscle tissues, indicating that their consumption likely causes similar microplastic exposure [77,78,80]. As the liquids covering the canned seafood were also reported to contain microplastics (6 items/mL in water and 0.006 to 5 items/mL in oil) [79,81], reducing the consumption of these liquids could contribute to exposure reduction (Figure 1). The findings are summarized in

Table 1. Amount and size of microplastics in seafood.

Seafood	Microplastic Amount	Size (µm)	Tissue/Body Part	References
Demersal and pelagic fish	828 total particles across 5 tissues	<100–>1000	Gills, gut, liver, muscle, skin	[55]
Tiger prawn (P. semisulcatus)	7–21 microplastics in muscle	<100–>1000	Muscle	[55]
White leg shrimp (L. vannamei)	1211 total microplastics; 193 ± 76.6 microplastics/g in gut	15–4686	Gut, gills, exoskeleton	[56]
L. vannamei	4.99 items/g	100–250	Exoskeleton	[57]
P. monodon	1.87 items/g	500–1000	Exoskeleton	[57]
Red mullet and Black sea shad	40% in gut, 7% in brain; 168 total microplastics for red mullet, 264 for black sea shad	50–200	Gut, gills, brain, muscle	[58]
Atlantic ditch shrimp	Experimentally ingested microbeads (200–2 × 1013 items/mL suspension)	0.1–9.9	Gut	[60]
Freshwater prawns	~33 microplastics per individual; ~32 microplastics/g in gut	<250–5000	Gut	[61]
Crab (P. pelagicus)	1.04 items/g in muscle	<100–500 mainly	Muscle	[65]
Green tiger prawn	0.62 items/g	<100–500 mainly	Muscle	[65]
Jinga shrimp	0.45 items/g	<100–500 mainly	Muscle	[65]
Hilsa shad	0.33 items/g	<100–500 mainly	Muscle	[65]
Bartail flathead	0.11 items/g	<100–500 mainly	Muscle	[65]
Crabs (mangrove wetland)	1.224–7.790 items/individual	1–5000	Whole body	[67]
Fish (mangrove wetland)	1.779–8.610 items/individual	1–5000	Whole body	[67]
Prawns (Australia)	0.8 ± 0.1 items/individual	38–1000 mainly	Whole body	[68]
Crabs (Australia)	1.6 ± 0.1 items/individual	38–1000	Whole body	[68]
Mussels (China)	2–11 items/g; 4–57 items/individual	5–5000	Whole body	[72]
Mussels (Belgium)	3–5 fibers/10 g	200–1500	Whole body	[71]
Dried anchovies	0.47–3.18 items/g	109–1006	Whole body	[75]
Dried ribbonfish	46 items/g	<500–5000	Whole body	[76]
Fresh ribbonfish	6.41 (gills), 6.20 (gut), 1.2 (muscle) items/g	<500–5000	Gills, gut, muscle	[76]
Dried hairfin anchovy	2.17 items/g	<500–5000	Whole body	[76]
Fresh hairfin anchovy	0.06 items/g	<500–5000	Whole body	[76]
Canned sardines/sprats	1–3 items per brand (only 4/20 brands positive)	>149	Edible parts	[77]
Canned tuna (Iran)	0.05–0.22 items/g	<50–5000	Muscle	[78]
Canned tuna (Ecuador)	4.4–6.9 items/g	1–50	Muscle	[79]
Canned liquid (oil/water)	0.006–6 items/mL	1–50	Liquid surrounding seafood	[79]

below.

4.1.2. Other Food Items and Food Packaging

Microplastic pollution is also present in various other food products. An investigation into the presence of microplastics in milk, soft drinks, honey, and beer produced in Ecuador found that microplastic concentrations ranged from 10 to 100 items per liter, with an average level of approximately 40 items/L [82]. The particle sizes identified spanned from 13.45 to 6742.48 μm for fibers, while fragments measured between 2.48 and 247.54 μm. The study explored the relationship between microplastic content in these products and the population density of their production sites, discovering that honey and craft beer made in densely populated cities contained higher amounts of microplastics, often exceeding 100 particles. However, no significant correlation was observed between the levels of microplastics and population density when all samples were considered [82]. This implies the presence of other factors during processing and packaging that could also affect the levels of microplastics in the food items [32]. Having said that, selecting food items with certified processing and handling techniques produced from relatively less-polluted places could contribute to lowering microplastic exposure (Figure 1).

Concerns about microplastic contamination in food have risen due to plastic food packaging. In a study by Du et al., commonly used polymer materials in take-out containers were examined, including polypropylene, polystyrene, polyethylene, and polyethylene terephthalate. The findings revealed that all types of take-out containers contained microplastics, with quantities ranging from 3 to 29 pieces per container [83]. The highest concentration of microplastics was found in polystyrene containers, particularly those with rough surfaces. Additionally, washing the containers with hot water did not impact the levels of microplastics present. This research suggests that the microplastics detected in take-out containers originate from both atmospheric deposits and the degradation of the container’s interior [83]. Another study supports this finding, showing that the average weight of isolated microplastics per pack is 12 mg for round-shaped containers, 38 mg for rectangular containers, and 3 mg for disposable plastic cups [84]. It highlights that new and disposable plastic containers can significantly contribute to human exposure to microplastics.

Additionally, six widely utilized containers for water and food, constructed from polypropylene, polyethylene terephthalate, and polystyrene, were subjected to treatments with distilled water and 10% and 50% ethanol under varying conditions [85]. The analysis revealed a particle range from 23,702 to 490,330 microplastics per liter, with 77 to 92% of these particles measuring less than 5 µm. Notably, the polypropylene container showed the most significant release of microplastics when exposed to 50% ethanol at a high temperature of 130 °C for 15 min, simulating the heating of fatty foods in a microwave [85]. The type of food and the heat applied were crucial factors that influenced the migration of microplastics in general. Furthermore, it was noted that direct microwave heating resulted in a markedly higher release of microplastics (534,109 particles per liter) [85]. A different study showed that soaking plastic materials—specifically packaging, cups, transparent containers, and expandable boxes—in hot water at 100 °C for 60 min released 1.07, 1.44, 2.24, and 1.57 million submicron and microparticles per mL, respectively, with a higher prevalence of submicron particles. Additionally, the thermal treatment modified the chemical structure of polyethylene packaging while causing negligible changes in polypropylene cups, transparent containers, and polystyrene expandable boxes [86]. Heating food in plastic containers also increases the leaching of plastic additives from the plastic. A study revealed that 42 intentionally added substances (IAS) and over 100 non-intentionally added substances (NIAS) were found leaching from microwaveable plastic food containers into food simulants [87]. The migration levels of significant IAS and NIAS were greater in 95% ethanol compared to other simulants, with a gradual decrease observed after multiple uses. Among the NIAS identified were polyethylene glycol oligomers of N,N-bis (2-hydroxyethyl) alkyl amines and isomers of hexadecanamide and oleamide [87]. However, since this review aims to provide practical recommendations for reducing human exposure to microplastics based on the major exposure routes identified in the literature, it does not discuss the associated exposure to plastic additives in detail.

A different study analyzed the presence and features of microplastics in 146 samples of take-out food, which included both solid foods and beverages such as bubble tea and coffee [88]. On average, there were 639 microplastic items per kilogram in the take-out food, with rice showing the highest concentration and coffee the lowest [88]. These studies provide strong evidence that take-out plastic containers are a significant source of microplastics. Placing hot food in these containers and heating them increases the release of microplastics. Replacing these containers with non-plastic alternatives, reducing the frequency of take-out, increasing dine-in options, and avoiding the placement of hot food or reheating food in plastic containers can help minimize microplastic ingestion (Figure 2). However, it is important to note that metal containers should not be used in microwaves. If microwaving is necessary, it is advisable to use glass or ceramic containers.

Kedzierski et al. found that extruded polystyrene microplastics contaminate food products at a level ranging from 4.0 to 18.7 items/kg of packaged meat. Analysis shows that these microplastics are likely to come from extruded polystyrene trays. These particles are difficult to remove by mere rinsing and are probably cooked before being consumed [89]. Research indicates that, during the simulated usage of six different brands of disposable breastmilk storage bags, there was a significant release of numerous micro-sized and submicron-sized particles, floccules (smaller than 300 μm), and fragments (ranging from 1 to 50 μm) [90]. Therefore, it is advisable to opt for fresh food items that are not pre-packaged and avoid using plastic packaging to store baby food (Figure 2). Recent studies have highlighted the issue of microplastics being released from plastic cutting boards. One research estimate suggests that approximately 100 to 300 microplastics or nanoplastics/mm can be released when cutting into the grooves of the board. In scratched areas, this number could rise to around 3000 particles per square millimeter with each cut [91]. These microplastics may ultimately be consumed by humans during food preparation. The substitution of plastic cutting boards with wooden ones could lower this exposure. Although wooden cutting boards might be contaminated with microplastics, no studies have confirmed this. Research comparing microparticle emissions from polyethylene, polypropylene, and wooden cutting boards during repeated chopping observed that wooden boards released microparticles; however, it did not specify whether microplastics were present [92].

4.1.3. Drinking Water and Beverages

Microplastics were also detected in bottled water. In Germany, researchers examined bottled water from both disposable and refillable plastic containers, as well as from beverage cartons, for microplastic contamination [93]. The disposable bottles showed an average of 14 particles per liter, while the refillable versions contained an average of 118 particles per liter, indicating that the latter have up to eight times the microplastic content of the former and ten times more compared to beverage cartons [93]. Another study by Mason et al. revealed an average of 10.4 microplastics per liter in 259 samples of bottled water sourced globally. These particles measured greater than 100 µm. When including smaller particles sized between 6.5 and 100 µm, the total microplastic count in the bottled water reached 325 particles per liter. Fragments and fibers were the predominant types of microplastics identified [94]. Zhou et al. conducted a study on 23 different bottled water brands in China to examine microplastic contamination with sizes greater than 25 μm. Their research identified two types of microplastics, fibers and fragments, along with 11 distinct polymer types. The microplastics varied in size from 0.025 to 5.000 mm, and their quantities were observed between 2 and 23 particles per bottle [95]. The researchers suggested that the source of microplastic contamination could be linked to the initial water source or shed particles from the bottle’s packaging. The projected daily ingestion rates of microplastics were estimated at 0.274 microplastics/kg per day for adults and 0.600 microplastics/kg per day for children [95]. A study conducted in Malaysia found that eight different brands of bottled water contained microplastics, with concentrations varying from 8 to 22 particles per liter [96]. The overall average was calculated to be 11.7 particles per liter. The most prevalent particle sizes ranged from 100 to 300 μm, making up roughly 31% of the microplastics identified in the bottled water samples [96].

Research carried out on bottled water available in China found that the typical concentration of microplastics in these products was 72.3 pieces per liter, surpassing the levels found in tap water, which measured 49.7 pieces per liter [97]. The predominant types of microplastics observed were films, primarily made up of cellulose and polyvinyl chloride. A separate study evaluated microplastics across nine different bottled water brands in Hong Kong [98]. It found that the average concentration of microplastics larger than or equal to 50 µm in the bottled water samples ranged from 8 to 50 particles per liter, whereas those smaller than 50 µm varied from 1570 to 17,817 particles per liter. Notably, the levels of microplastics in mineral water samples were substantially higher than those in distilled and spring water. Additionally, three local tap water samples were analyzed and compared to the bottled water, revealing a lower presence of microplastics in the tap water samples [98]. In a study conducted by Weber et al. in Germany, water samples were collected from a commercial property, a residential building, an apartment, a single-family home, and an educational institution. The findings revealed that no microplastics or colored particles and fibers were found at house connections or the transfer station. In addition, there were no microplastics found in any samples collected from drinking taps [99]. To minimize microplastic exposure from water consumption, it is advisable to reduce the frequency of drinking bottled water and to choose tap water whenever a water dispenser that provides filtered water directly (not from a large plastic bottle) is available. In countries where tap water can be directly consumed, it could be a better choice than bottled water. The choice of water containers could contribute to reducing microplastic exposure. Since plastic bottles have been associated with higher microplastics, metal and glass containers could be used as substitutes.

Although paper cups are often considered safe for holding drinking water from dispensers, recent studies have revealed some disturbing results. The interior of these cups is coated with a hydrophobic film primarily made of plastic (polyethylene) and, at times, copolymers. Research assessed how these films degrade when exposed to hot water (85–90 °C). As the films broke down, various ions, including chloride, fluoride, nitrate, and sulfate, leached into the water within the paper cups [100]. In a particular study, roughly 25,000 microplastic particles, measuring around one micron, were found in just one cup of 100 mL of hot water within 15 min. Scanning electron microscopy revealed that there were about 102.3 × 10⁶ sub-micron particles per milliliter in the same volume of liquid [100]. By analyzing the microplastics released from 90 types of disposable cups in the market, which included polystyrene cups, polyethylene-coated paper cups, and polypropylene cups, through daily use, a study confirmed that microplastics were found in all tested cups [101]. The released microplastic particles were primarily irregular in shape and mostly smaller than 20 μm. The quantities of these released microplastics ranged from 838 to 5215 particles/L for polystyrene cups, 675 to 5984 particles/L for polyethylene-coated paper cups, and 781 to 4951 particles/L for polypropylene cups, when filled with pure water at 95 °C for 20 min [101]. This suggests that hot water in polymer-coated paper cups might contain as many, or even more, microplastics than plastic disposable cups. Zhang et al. investigated plastic-coated paper cups made from polyethylene from various manufacturers to assess their use for drinking hot water. Their research revealed that the average concentration of microplastics in the water extracts from five paper cups was about 12.9 × 10⁵ particles per liter, with sizes ranging from 1 to 60 μm in length. The study identified the following three types of microplastic particles: polyethylene, polyamide, and some unidentified microplastics [102]. These studies suggest that the use of paper cups to contain hot water discharged from water dispensers could lead to significant microplastic intake. Where these disposable cups need to be used, they are advisable only for cold or room-temperature water. Non-disposable metal or glass containers are better options, as they could reduce the amount of waste disposable cups generated while reducing microplastic ingestion. In addition, filter-type water dispensers have the advantage over water dispensed from refillable containers, which have been reported to contain substantial microplastics [93]. An assessment of membranes made from cellulose acetate, polycarbonate, and polytetrafluoroethylene, all possessing a uniform nominal pore size of 5 μm, showed the successful elimination of polyamide and polystyrene microplastics, with sizes between 20 and 300 μm. They achieved a mass removal efficiency of over 94% for microplastics at a concentration of 100 mg/L [103]. This suggests that the membrane filtration of tap water could reduce microplastic intake through water consumption. The effectiveness of membrane filtration was also demonstrated by the successful removal of 78–86% of polyvinyl chloride microplastics and 94–100% of polyethylene terephthalate microplastics from spiked drinking water through a point-of-use microfiltration system [104].

Food filter bags made from plastics such as nylon 6, polyethylene, polyethylene terephthalate, and polypropylene, commonly used for packaging beverages that require straining, contribute to microplastic exposure. Three varieties of non-woven and woven filter bags in the market were examined in a study [105]. After being soaked, up to 94% of these bags emitted microplastics, with no significant relationship identified concerning the soaking conditions. The majority of the released microplastics were small fragments and particles, with a few being fibrous in nature, measuring between 620 and 840 μm. Among the types assessed, the woven nylon 6 filter bags presented the least likelihood of microplastic release [105]. Fard et al. reviewed the microplastics released from tea bags and found that plastic or composite tea bags released varying amounts of micro- and nanoplastics, ranging from 10⁵ to 10⁶ particles per liter of water upon steeping at 95 to 100 °C for 5 min, with particle sizes spanning over a wide range of <0.22 to 150 µm [106]. Banaei et al. studied compostable polylactic acid tea bags in Spain, also steeped at 95 °C. Using scanning electron microscopy and nanoparticle tracking analysis, they detected approximately 10⁷ micro- and nanoplastics per bag, with sizes predominantly between 159.5 and 395.1 nm [107]. There is currently a lack of studies on the microplastics released from steeped paper teabags, but avoiding plastic (biodegradable and non-biodegradable) teabags could contribute to reducing microplastic exposure. Nonetheless, microplastics have also been detected in loose tea leaves. About 3000 micro- and nanoplastics per liter of tea were detected from a 200 mL tea drink prepared from 2 g of loose tea leaves [108]. Since both tea leaves and tea bags contain microplastics, opting for loose tea leaves avoids additional exposure to microplastics from tea bags.

Table 2. Microplastics in bottled water, cups, and tea bags.

Source	Microplastic Level (Particles/L)	Size (µm)	Reference
Bottled water (Germany)	Disposable: 14; Refillable: 118; Cartons: ~12	5–20 mainly	[93]
Bottled water (global samples)	>100 µm: 10.4; Total (6.5–100 µm): 325	6.5–>100	[94]
Bottled water (China)	2–23 particles per bottle	>25	[95]
Bottled water (Malaysia)	8–22; Average: 11.7	100–300 mainly	[96]
Bottled vs. tap water (China)	Bottled: 72.3; Tap: 49.7	10–50 mainly	[97]
Bottled water (Hong Kong)	≥50 µm: 8–50; <50 µm: 1570–17,817	<50 and ≥50	[98]
Tap water (Germany)	0 (no microplastics found)	N/A	[99]
Paper cups (hot water, 100 mL)	~25,000 particles per cup (~250,000/L)	~1	[100]
Disposable cups	Polystyrene: 838–5215; Polyethylene-paper: 675–5984; Polypropylene: 781–4951	<20 Mainly	[101]
Paper cups (5 brands)	1.29 × 106	1–60	[102]
Tea filter bags	Not quantified (up to 94% released MPs)	620–840	[105]
Plastic tea bags	105–106	<0.22–150	[106]
Compostable PLA tea bags	~107 particles per bag	0.1595–0.3951	[107]
Loose tea leaves	~200–500 particles/g	Not specified	[108]

summarizes the microplastics in bottled water, cups, and tea bags.

4.2. Reducing Exposure Through Inhalation

4.2.1. Indoor Air Filtering

Multiple studies have indicated a higher risk of microplastic exposure in indoor air. A study involving 30 volunteers in Shanghai, China, collected inhaled indoor aerosol (HIA) and human exhaled breath (HEB) samples from each participant. Microplastics were detected in all samples, averaging 43 (range of 11–92) items/m³ for HIA and 12 (range of 3–28) items/m³ for HEB [109]. Moreover, the dominant components in all samples were small fragment- and fiber-shaped microplastics. It was estimated that the daily intake of HIA is roughly 704 microplastics, most of which would be deposited in the airway, with 526 particles, whereas 178 particles could be discharged daily via HEB [109]. Liao et al. studied the presence of microplastics in both indoor and outdoor settings within urban and rural regions of a coastal Chinese city. They found that the concentration of microplastics in indoor air (1583 ± 1180 items/m³) was significantly higher, by an order of magnitude, compared to outdoor air (189 ± 85 items/m³) [110]. Additionally, microplastic levels in urban areas (224 ± 70 items/m³) exceeded those in rural zones (101 ± 47 items/m³). The majority of airborne microplastics measured were less than 100 µm in size, with fragments being the most common shape, unlike fibers [110].

Research carried out in coastal California revealed that microplastics are present in the air, showing that indoor air contains significantly higher levels than outdoor air [111]. Specifically, the concentration of microplastic fibers was measured at 3.3  ±  2.9 fibers and 12.6  ±  8.0 fragments per cubic meter indoors, in contrast to outdoor levels of 0.6  ±  0.6 fibers and 5.6  ±  3.2 fragments per cubic meter. While the length of microplastic fibers showed no considerable difference between indoor and outdoor environments, the size of indoor microplastic fragments, averaging 58.6  ±  55 µm, was notably smaller than the outdoor counterparts, which averaged 104.8  ±  64.9 µm [111]. A study conducted in 39 major cities across China collected dust samples from both indoor and outdoor settings [112]. The results revealed polyethylene terephthalate microplastics in all samples at notably high concentrations, ranging from 1550 to 120,000 mg/kg indoors and from 212 to 9020 mg/kg outdoors. Additionally, approximately 70% of the samples contained polypropylene microplastics, with a median indoor level of 4.6 mg/kg and a median outdoor level of 2.0 mg/kg [112]. Fibers were identified as the predominant shape of these suspected microplastics, with polyester (including polyethylene terephthalate) being a significant component found in the dust. Importantly, indoor dust represents a significant source of microplastic exposure for humans, contributing to an average daily intake of 17,300 ng/kg body weight of polyethylene terephthalate microplastics in children [112].

Given that many of us spend about 90% of our time indoors, it is essential to clean indoor air to reduce exposure to microplastics. Indoor air filters have been specifically created to eliminate various pollutants from the indoor environment. These appliances work by circulating the air within a space through several filters, capturing impurities such as microplastics found in the air [113]. Manufacturers of some of these devices assert that their technologies can filter out particles as tiny as 0.003 µm, which is significantly smaller than the smallest microplastic particles detected, implying that they are effective in removing all potential microplastics. This advancement relies on the HyperHEPA filtration system [114]. Meanwhile, other manufacturers maintain that their air purifiers equipped with HEPA filters can filter out particles as small as 0.3 µm, and those utilizing HEPASilent technology, which integrates electrostatic filters with HEPA filters, can capture particles down to 0.1 µm (Figure 3) [114].

Minimizing airborne microplastics indoors contributes to purifying indoor air; however, filters require regular replacement or cleaning. Consequently, the microplastics that are trapped by these filters are essentially transferred from the indoor space to the outside environment. To effectively minimize airborne microplastics in indoor settings, it is essential to start with regular cross ventilation (Figure 3). This should be complemented by consistent vacuuming of the floors, ideally with a central vacuum system that expels contaminants away from cleaned areas [115]. If a central system is not feasible, using vacuum cleaners equipped with HEPA filters is recommended to stop pollutants from re-entering the environment (Figure 3) [114]. Since carpets and polyvinyl chloride or other plastic flooring can either hold or emit microplastics, replacing them with natural wood or ceramic alternatives is advisable. Additionally, any wooden floors, furniture, and coatings on walls and paints should avoid synthetic additives.

4.2.2. Reduction or Avoidance of Smoking

Smoking has been recognized as a potential route for the inhalation of microplastics. In a study conducted in Zhuhai City, China, researchers collected bronchoalveolar lavage fluid (BALF) samples from 17 smokers and 15 nonsmokers [116]. An active smoking model was utilized to assess the impact of smoking on the inhalation of microplastics. Microplastics were detected in all BALF samples analyzed. Smokers exhibited greater levels of microplastics (25.86 particles/g), along with higher levels of polyurethane (11.34 particles/g) and silicone (1.15 particles/g), compared to nonsmokers. The majority of microplastics measured between 20 and 80 µm in size, and the median diameter was 34 µm. In the simulated cigarette smoking model, the levels of microplastics (9.99 particles/L), polyurethane (4.66 particles/L), and silicone (2.78 particles/L) were found to be significantly higher in the cigarette smoke group compared to the control group [116]. Currently, there is only one study that highlights the exposure to microplastics through cigarette smoking; thus, the evidence is limited. However, reducing smoking and minimizing exposure to cigarette smoke could potentially decrease the inhalation of microplastics (Figure 3).

4.2.3. Wearing Facemasks

There has been debate about whether facemasks shield wearers from microplastics or if they contribute to microplastic exposure. A study examined how five different types of masks (activated carbon, cotton, fashion masks, N95, and surgical) influence the likelihood of people inhaling microplastics and phthalates while wearing them [117]. The residual levels of seven phthalates were found to range between 296 and 72,049 ng/g, with a median concentration of 1242 ng/g. Surgical masks showed the lowest median phthalate concentration at 367 ng/g, whereas fashion masks had the highest at 37,386 ng/g. Individuals inhaled between 25 and 135 microplastics indoors and 65 and 298 microplastics outdoors, after wearing different masks for 6 h [117]. The estimated daily intake of phthalates, considering both indoor and outdoor exposure through inhalation and skin contact, varied from 1.2 to 13 ng/kg body weight/day for indoor conditions and 0.43 to 14 ng/kg body weight/day for outdoor conditions [117]. Therefore, surgical masks offer significant protection, whereas cotton and stylish masks lead to a higher risk of microplastic and phthalate exposure, whether indoor or outdoor, compared to not using a mask.

Based on the types of microplastic polymers found, another study indicates that the presence of microplastics in the nasal cavity is predominantly linked to general exposure to airborne microplastics rather than the use of face masks [118]. Over a period of five working days, six different commercial face masks were tested, each used for eight hours a day. The results showed an average concentration of 28.3 ± 15.6 microplastics detected in a 5 mL nasal solution, mainly in the 20–300 µm size range. This finding stands in stark contrast to the research conducted by Zhang et al., which showed that the use of surgical masks led to a rise in the quantity of microplastics found in nasal lavage fluid, with particle sizes predominantly <100 µm, in comparison to 100–200 µm from natural exposure [118,119]. The longer the masks were worn, the greater the microplastic concentration observed. Current research on microplastic exposure from mask wearing is limited, making it unclear whether wearing a mask decreases or increases overall exposure to microplastics. However, the protective benefits of wearing a mask are considered to outweigh any potential adverse effects linked to higher microplastic exposure. This is particularly true for protection against airborne diseases and harmful chemicals or pollutants, as long as the appropriate type of mask is used. Research has shown that reusing disposable masks can result in a notable discharge of microplastic fibers, which could potentially enter the respiratory system. Additionally, the amount of microplastic fibers released escalated with extended external friction, especially when masks were kept in pockets [120]. To reduce the inhalation of microplastics from masks, it is important to prevent the reuse of disposable masks and to store them properly between uses.

4.3. Reducing Exposure Through Dermal Contact

Since dermal contact is not a significant exposure route to microplastics, there is considerably less research on this topic. Nonetheless, microplastics on the skin could release additives such as flame retardants. Human contact with total polybrominated diphenyl ethers and hexabromocyclododecane through skin exposure to microplastics was measured between 0.02 to 22.2 ng per kg body weight per day and 0.01 to 231 ng per kg body weight per day for adults and between 0.02 to 6.27 ng per kg body weight per day and 0.2 to 65 ng per kg body weight per day for toddlers [121]. The level of skin exposure to these compounds in microplastics is considered significant.

Particles that enter the body through the skin must navigate through layers of the epidermis to reach the capillaries within the dermis, where they can be transported throughout the body via the bloodstream [122]. In comparison to ingestion and inhalation, the exposure to microplastics through skin contact has received less research focus, primarily because the skin barrier typically prevents the uptake of particles larger than 100 nm [50]. Nonetheless, nanoplastics, which are smaller than 100 nm, represent a growing environmental concern and may have the ability to penetrate the skin barrier [123]. Microbeads that are 40 nm in size or smaller can enter epidermal Langerhans cells surrounding hair follicles, whereas larger particles, such as those sized 750 nm and 1500 nm, have limited absorption [124]. The use of personal care items like exfoliators, hand cleansers, and toothpaste is the main cause of dermal exposure [125]. As only microplastics of limited sizes can pass through the skin, absorption through the skin is more associated with the uptake of liberated monomers or organic plasticizers, such as bisphenol and phthalates [126]. While it seems feasible to minimize dermal contact by carefully selecting personal care products that do not contain microbeads, the extent of skin exposure associated with the use of microbead-containing personal care products and the effectiveness of reducing this exposure by avoiding these products remain uncertain due to limited studies.

5. Potential Reduction of Microplastic Toxic Effects Through Antioxidants

Microplastics trigger oxidative stress by generating reactive oxygen species and disrupting cellular redox balance, leading to cellular damage and inflammation. Upon ingestion or exposure, microplastics interact with biological membranes and intracellular components, causing mechanical stress and initiating oxidative stress pathways [7]. Additionally, microplastics often carry hazardous pollutants such as persistent organic pollutants, heavy metals, and per- and polyfluoroalkyl substances, which further amplify reactive oxygen species production and exacerbate oxidative damage [127,128]. Recent research on the toxicity of microplastics in mammals has primarily focused on polystyrene, with less emphasis on polyethylene and polypropylene. In studies conducted in living organisms, researchers typically use mice or rats, and exposure occurs mainly through ingestion [7]. Conversely, in laboratory experiments, various cell lines are utilized, with intestinal cell models being the most frequently studied [129]. The toxicological impact of microplastics depends on their size and specific biomarkers. For instance, polystyrene microplastics administered at concentrations ranging from 1.49 × 10⁶ to 4.55 × 10⁷ particles per mouse did not produce noticeable adverse effects. However, dosages between 0.01 mg/day and 0.15 mg/day led to adverse reactions [6]. In testing with cell lines, polystyrene microplastics at a concentration of 10 µg/mL did not cause harmful effects, whereas levels from 0.01 µg/mL to 5000 particles/mL did induce negative outcomes, varying by cell type. Polyethylene microplastics, when dosed at 0.125 mg/day, typically elicited negative responses in mice, and polypropylene microplastics at a concentration of 5000 particles/mL resulted in adverse reactions in THP-1 macrophage cells [6].

A study assessed the protective effects of various antioxidants, including lycopene, citric acid, and chlorella, against the harmful consequences of microplastic consumption in Clarias gariepinus, utilizing histopathological indicators [130]. The study involved the following five experimental groups: a control group on a standard diet, a group subjected to 500 mg/kg of microplastics along with the standard diet, and three groups receiving microplastics paired with either 500 mg/kg of lycopene, 30 g/kg of citric acid, or 50 g/kg of chlorella added to their standard diet. The histological evaluation showed that microplastics led to damage in the kidney, liver, and intestinal tissues. The detrimental effects on the kidney, liver, and intestinal histopathology were either completely or partly mitigated by the addition of dietary lycopene, chlorella, or citric acid [130]. In a study by Chen et al., the effects of various doses of exogenous glutathione were assessed on the physiological characteristics of rice plants subjected to two types of microplastics, namely polyethylene terephthalate and high-density polyethylene, in the root zone [131]. The results indicated that all rice seedlings experienced a significant growth reduction when compared to the control group. The treatment with glutathione notably enhanced the following growth parameters: weight of 100 grains increased by 9.4%, plant height increased by 5.75%, shoot fresh weight increased by 8.8%, shoot dry weight increased by 13.7%, root fresh weight increased by 19.22%, and root dry weight increased by 25.52%, relative to control plants [131].

A separate study explored how different types of microplastics, including polyvinyl chloride, polyethylene terephthalate, polypropylene, and polyamide, affect rice plants grown hydroponically [132]. The addition of ascorbic acid showed a significant reduction in damage caused by microplastics, leading to improvements in root and shoot biomass, photosynthetic activity, and chlorophyll levels. The application of ascorbic acid improved the negative effects of microplastics, increasing the photosynthesis rate by 14.4% in the polyvinyl chloride treatment, 10% in the polypropylene treatment, and 9.5% in the polyethylene terephthalate treatment. Additionally, ascorbic acid elevated levels of beneficial metabolites while decreasing markers of lipid peroxidation and oxidative stress [132].

Currently, research on antioxidant supplementation to mitigate the toxic effects of microplastics is quite limited, and the available studies have focused primarily on plants and fish. There are no available studies on human cell lines or mammals. While these studies offer hope for potentially reducing microplastic toxicity through antioxidants, it remains too early to draw any conclusions about their effectiveness in humans.

6. Conclusions

Microplastics can enter the human body through ingestion and inhalation, with limited evidence indicating potential exposure via skin contact. A significant concern regarding microplastic interaction with the skin is the possible leaching of harmful additives; however, available studies are insufficient to assess the associated risks. While nanoplastics may potentially penetrate the skin, further evidence is needed to validate this claim. Current research emphasizes that seafood, plastic packaging, and drinking water are primary sources of microplastic ingestion. Consequently, the following measures could help reduce exposure: (1) consume only the muscle portions of fish and crustaceans while minimizing the intake of non-muscle parts; (2) consider moderation in consuming crustaceans, mollusks, and anchovies; (3) decrease the consumption of liquids in canned seafood; (4) store harvested mussels in clean water for depuration prior to ingestion; (5) avoid using plastic take-out containers, especially for hot food, and refrain from microwaving them; (6) opt for non-plastic alternatives to take-out containers; (7) use wooden cutting boards instead of plastic ones; (8) prefer tap or filtered tap water over bottled water; (9) refrain from pouring hot water into disposable paper cups coated with polymers; and (10) select tea bags made of paper rather than plastic. Indoor air pollution and smoking significantly increase microplastic inhalation exposure. To mitigate this exposure, the following strategies are recommended: (1) utilize indoor air filters, preferably equipped with HyperHEPA filtration systems, to trap airborne microplastics; (2) ensure regular cross-ventilation and vacuuming; and (3) reduce smoking and limit exposure to cigarette smoke. Antioxidant supplementation has shown encouraging results in plants and fish for alleviating oxidative stress and toxic effects associated with microplastic exposure, suggesting potential benefits for humans. Nonetheless, further research is necessary to determine the efficacy of antioxidant supplementation in reducing microplastic toxicity in mammals. Additionally, it is unclear whether the protective benefits of masks against microplastics compensate for potential microplastic exposure from the masks themselves. More studies are also required to establish the risks of microplastic exposure to active and passive smokers. While minimizing exposure can diminish health risks related to microplastics, it does not offer a long-term solution. A comprehensive approach should prioritize moving away from traditional plastics and the linear plastic economy to decrease environmental plastic levels.