Meteorological observations worldwide reveal significant increases of heat-stress conditions and future climatological scenarios report that we should expect far worse situations even in the most optimistic projections [1
]. Workers, and above all outdoor manual workers, represent an important part of the population potentially vulnerable to heat stress [3
]. In particular, work that involves high levels of physical exertion—such as heavy lifting and manual labor carried out for example by farmers, construction workers, fire-fighters, miners, soldiers, and manufacturing workers operating near artificial heat sources—are particularly affected since individuals tire faster and metabolize heat less effectively under exertion [3
]. Workers are often exposed for many hours to direct solar radiation or artificial radiant heat, and in several cases wearing personal protective clothing and equipment that significantly aggravate heat stress by limiting body heat loss. An advanced working age or the potential interaction between heat and chemical substances (i.e., pesticides and fertilizers), used i.e., in agricultural activities, represent other important heat-related vulnerability factors. For economic reasons, workers may need to work during hot weather conditions, which impose an occupational heat stress; it is a public health issue. However, appropriate adaptation strategies could help to avoid heat-related health problems, and also limit the typical productivity loss that occurs during the warmer period of the year [7
]. Although workers contribute enormously to economic growth, they are often overlooked in discussions about the effects of heat [9
], and specific heat warning systems for occupational purposes are actually unavailable internationally.
An accurate and timely heat–health warning system (HHWS) represents one of the core elements nested in a wider Heat–Health Action Plan, which encompasses and directs all preventive measures to be taken to protect the population from the effects of environmental heat exposure [9
]. At present, HHWSs aim at protecting the general population or people considered most vulnerable, such as the elderly population [12
], even if in recent studies [10
] young workers were found to be as vulnerable and at increasing risk of occupational injuries with high temperatures. Various metrics to define the effects of heat on health have been developed [9
], based on different thermal (i.e., single-metric based on air temperature or heat stress index; heat budget models; air mass-based synoptic climatological approaches) and health indicators (generally mortality data, but also morbidity indicators could be used if available). In this way, different heat threshold levels based on epidemiological (i.e., city-specific heat-related mortality thresholds) or climatological (i.e., specific percentiles of the local distribution of minimum and maximum temperatures) evidences, or even based on heat stress levels assessed through specific thermal stress indices, have been developed and are currently used to issue heat warnings in HHWSs [9
]. Concerning the occupational sector, a HHWS should be more focused on heat stress than mortality events or other health indicators addressed to the general population. This is because heat stress for workers represents a public health concern [5
] and worker health and performance are affected at much lower environmental heat strain levels than those directly associated with higher mortality. When working in the heat, skin blood flow and sweat rate increase to allow for heat dissipation to the surrounding environment (thermoregulatory adjustments), thus increasing risk of heat-related injuries, kidney diseases and generally, physiological strain leading to dehydration [18
]. A recent study [20
] revealed that about 70% of workers initiate work with a suboptimal hydration status, meaning that workers are dehydrated at onset of work and that rehydration from day to day may be a bigger issue than failure to drink during the working shift. The higher heart rate associated with dehydration signifies an overall elevation of cardiovascular strain [21
]. Dehydration may have an even larger impact on performance in cognitive occupational settings where people are exposed for prolonged periods to high heat stress levels and fail to prevent hypo-hydration [20
]. Surely, a good adaptation to heat can help to prevent many negative consequences, even if it has recently been highlighted that heat acclimation may not be sufficient to protect against hyperthermia when complex tasks are performed [22
]. Thus, the availability of timely heat stress warnings calibrated on specific work activities and accounting for the clothing worn would make it possible to reduce heat-related performance losses, especially in the case of prolonged heat exposure.
Due to the different needs of the occupational sector compared to the general population, a HHWS for occupational purposes should have some main characteristics. In particular:
It should be personalized; that is, based on the physical demands of the job as well as on workers’ physical, clothing, and behavioral characteristics and on the work environment;
it should include short-term suggestions useful to help heat adaptation for workers;
it should contain long-term heat risk information for planning/organizing work, which is useful for employers, organizations, and operators in charge of safeguarding health and productivity in various occupational areas.
To achieve this goal, a meteorological forecasting model for different lead times (with forecasts up to about one month) is necessary, as well as the use of a thermal stress indicator able to provide detailed information in various situations. Then, the metric used should account for the level of physical activity performed by a worker, which will obviously be influenced by personal physical characteristics (e.g., weight and height), the clothing worn, and the working environment, differentiating between a worker exposed to solar radiation, or other heat sources, and a person working in the shade.
At the international level, there is presently no example of a HHWS specifically targeting workers and capable of meeting the main characteristics listed above. At European level, an important contribution on this topic has been provided by the European project “Integrated inter-sector framework to increase the thermal resilience of European workers in the context of global warming” (HEAT-SHIELD) [23
] that aims to develop solutions to protect the health and productivity in workplaces from excessive heat in the context of climate change. In 2017, a first prototype of an occupational HHWS for entire Europe for a timeframe of four upcoming weeks was developed within the frame of HEAT-SHIELD. In 2018, an online open access service (website platform) was officially launched to help industry and society anticipate threats by heat stress to workers’ health and productivity.
The aim of this paper is to present and describe the characteristics of the website platform “HEAT-SHIELD occupational warning system” [24
], currently operating for the entire Europe and representing one of the main outcomes of HEAT-SHIELD.
The HEAT-SHIELD platform [24
] developed within the frame of the European Project HEAT-SHIELD and described in this study represents the first step to fill the lack of international heat warning systems specifically addressed to occupational sectors. This website platform was officially launched in 2018 and is currently operating for about 1800 European localities. It represents the first international example of personalized short- and long-term heat risk forecasts with useful heat-related adaptation information for workers and stakeholders in charge of safeguarding workers’ health and productivity.
The main characteristics of the HEAT-SHIELD platform are listed below and make this heat warning system original and unique:
the HEAT-SHIELD platform is multilingual.
The local-heat-stress-risk forecast is “customized” based on:
the worker’s physical characteristics (specifically height and weight),
the physical activity level,
the clothing or PPE worn during work,
the work environment (outdoors in the sun or shade),
also taking into account whether the worker is acclimatized or not to the heat.
The short-term heat risk forecast (5-day forecasts) includes behavioral recommendations related to how much hydration (water intake) and rest (work breaks) during the worst (in term of heat stress) hour of the day.
Long-term heat risk forecasts are available up to just over one month (46 days).
Currently the website platform is available in six languages (English, Italian, Slovenian, French, Portuguese and German) and will be further implemented in other languages. This characteristic is of great importance especially in the occupational field because most European countries are typically multicultural. It is indeed known that foreign workers may have a real difficulty in understanding the local language with consequent important repercussions on the perception of the heat risk in the workplace [64
]. As reported in a recent review on the existing HHWSs in Europe [17
], one of the main communication limits of these systems is that the warnings are generally issued in the local language of each country in addition to (in very few countries) English.
The non-customized heat stress forecast output (the maps of the weekly maximum probability of exceeding the daily WBGTsun
threshold of 27 °C) is simplified, generalized information valid for the whole Europe and accessible to everyone without any registration information. However, this information has the limitation of highlighting the potential heat risk mainly in southern Europe, displaying a clear latitudinal gradient typically resembling the air temperature gradient. The scientific literature [66
] has shown that local populations are acclimatized to their local climate and respond to heat stress differently. A solution to try to solve this limitation would be to collect data on the perception of heat stress in the occupational sectors in various geographical areas with different climatic characteristics. In this way, the WBGT thresholds might be recalibrated accounting for geographical adaptation. The main aim of the very general information provided by the non-customized outputs is to motivate the user to register on the HEAT-SHIELD platform to obtain personalized information on heat stress risk calculated by using a tailored WBGT threshold based on individual worker characteristics and the workplace environment. The personalization of the forecast certainly represents an ambitious challenge to improve the generic information already available and provided by the main meteorological services and that need to correctly interpret each personal situation. This customized approach is essential in occupational settings due to the high variability of environmental conditions and job/task activities, which results in a strong heterogeneity of the thermal stress exposure with direct repercussions on workers’ health and productivity. However, it must also be considered that, in common practice, workers accustomed to carry out specific work tasks repetitively, might make a self-evaluation in a way that underestimates the work effort and therefore the heat-related job risk perception. This situation might include some bias and distort the efficiency of the strategies to counteract heat stress. Distortion might also depend on socio-cultural aspects, such as the dietary habits that underlie the maintenance of a good level of hydration and nutrition. For example, people of Muslim origin are at greater heat-related health risk during the Ramadan period [69
]. On the other hand, a natural reaction to heat of a worker is to reduce their physical activity, that is a self-pacing or autonomous adaptation which reduces the body’s internal heat production but also the hourly work capacity [71
A strength of the developed website platform relates to its ability to provide hydration and work/break schedule recommendations in the short term. Taking breaks in shady or cool areas as well as suggestions on hydration (water consumption) during working time according to specific heat stress conditions and physical efforts represents a fundamental heat-related adaptation method recommended by the ISO [36
] and other governmental agencies [19
]. Moreover, the platform also includes e-mail alerts that represent important adaptation strategies to timely counteract heat stress conditions and safeguard the workers’ health and productivity.
The HEAT-SHIELD platform is a potentially very useful tool because heat stress is significantly increasing in many geographical areas worldwide, with strong effects also in European cities [74
]. In addition, heat stress is expected to increase significantly in the next years because of climate change [1
] also in areas where the worker population is not used to fighting this phenomenon [75
], such as central-northern European countries.
At the moment, the HEAT-SHIELD platform is the only example of a website platform providing such a comprehensive collection of information. Nevertheless, there are already a few interesting smartphone applications in place that inform workers about precautions against outdoor heat stress. These include the OSHA NIOSH Heat Safety Tool [76
] and the ClimApp [77
] device currently in an advanced stage of development by several HEAT-SHIELD partners. These applications are, however, not able to provide long-term forecasting information that is particularly useful for planning issues. Precisely for this reason, the HEAT-SHIELD website platform is based on the extended range ensemble forecasts of the ECMWF that enables customized heat stress risk up to over a month. In this way, useful information for employers, organizations and operators in charge of safeguarding health and productivity in various occupational areas are provided, calibrated with greater precision, the interventions to be taken according to the subjective characteristics of the worker and other situations in which the workers are involved. A further interesting feature of the HEAT-SHIELD platform is the possibility for real-time verification of the heat stress risk situation by modifying some characteristics, for example, by varying the work environment (e.g., working in the shade) or the clothing worn, in this way planning the best actions to counteract the effects of the heat in the long term. Certainly, there is a need of further validation including the worker’s health component linked to the information provided by the HEAT-SHIELD platform. This might be done by processing the subjective information collected by the self-administered questionnaire developed within the frame of the HEAT-SHIELD project. They have already been used in several European countries for gathering evidences on workers’ risk perception of heat stress in the workplace and potential productivity losses due to extreme heat. For example, based on a preliminary investigation [78
] carried out during the summer months of 2017 and 2018 on some workers engaged in Italy in construction and agriculture sectors, results revealed agreements between the ISO-standard WBGT thresholds associated with specific work efforts and the worker’s thermal stress perceptions for high WBGT values (WBGT > 30 °C). Conversely no agreements were observed for lower WBGT values. In the latter case, workers declared a heat stress level (from low to more often moderate heat stress) even if the ISO-standard WBGT threshold for that activity level does not recommend critical heat-stress conditions. For this reason, if data collected also in other countries during the summer of 2019 and the following summers confirm these preliminary results, the recalibration of the ISO-standard WBGT thresholds may be desirable, also including lower critical values which, however, may represent a health problem. Furthermore, through the case studies planned as part of the HEAT-SHIELD project, other health/physiological data of workers are being collected that could be of great help for a worker’s health validation in relation to heat stress in workplaces.
Since the HEAT-SHIELD project started (January 2016), some stakeholder meetings presenting the HEAT-SHIELD platform have already been organized during the years of 2018 and 2019 in several European countries, and other meetings are scheduled in different countries by the end of the project (December 2020). One of the main objectives of these meetings, in which employers, workers, worker safety representatives, prevention, protection service managers and competent doctors took part, was to obtain immediate feedback on the HEAT-SHIELD platform. Initial user feedback suggest that there is potential for further improvements, with new procedures/suggestions aimed to provide increasingly detailed information useful for worker’s heat-related health prevention and reducing productivity loss. Trying to maximize employers’ involvement in the use of the HEAT-SHIELD platform is a priority since they are considered key elements among all stakeholders. In particular, employers are the main actors for regulating work activities (i.e., defining of the length of work shifts and relative work breaks, identifying of the days and working hours in which to carry out certain work activities, defining of the number of workers involved in specific work tasks, etc.) and are responsible for the workers’ health, without ever losing sight of the economic aspect linked to work productivity.
Field studies carried out also in the field of the HEAT-SHIELD project [14
] aimed at evaluating the responses of workers exposed to heat stress conditions during different work activities will be particularly useful for identifying the best heat-related adaptation strategies helpful to manage this hazard situation. For now, only recommendations on water consumption and work/rest breaks clearly described in reports provided by international organizations working on this topic are provided. However, other recommendations (i.e., the recommended clothing, or others) obtained by using other thermal-stress indicators, subjective information (i.e., age or gender), and detailed infographics related to specific occupational sectors, could also be integrated and included in an operational way in the HEAT-SHIELD platform to counteract the effects of heat. A more complex issue, on the other hand, concerns the possibility of personalizing the heat risk level based on pre-existing diseases or specific pharmacological treatments. Currently, information on the customized heat risk refers to a healthy worker and not where specific drugs are used; the situation should always and exclusively be evaluated by an occupational health physician.
In the near future, it will also be desirable to develop a system for monitoring work injuries to be updated in real time, to report heat-related injuries in order to activate timely emergency response interventions. In the current version, the website platform does not include heat stress thresholds based on the relationships between WBGT and injuries because only very few studies have investigated this relationship [82
]. In addition, the use of meteorological data for occupational heat stress assessment is actually limited because weather stations do not traditionally and directly measure some important climate factors useful for WBGT calculation [83
]. For this reason, results are not as obvious as those identified between several thermal indicators and some categories of the general population (e.g., the elderly) [85
]. In fact, in this latter case, city-specific thermal stress thresholds were identified, and in several cases, these thresholds were implemented in HHWSs addressed to the general population or the elderly [17
The current website platform relies on a probabilistic forecast model, which has the advantage of allowing long-term forecasts. It has, however, also some limitations such as the temporal resolution (it only provides a daily value). In particular, the intra-daily hourly heat stress risk forecast (i.e., morning, afternoon, evening, night) is not provided and the information is only available for a limited number of European localities (about 1800). For this reason, we are already working to implement the heat stress risk forecast in the short term for specific regions by using high-resolution (i.e., spatial resolution of 3–7 km) deterministic meteorological models. In this way, detailed information on an hourly basis will be obtained and personalized heat stress risk will be available for various times of the day in which workers can be engaged. Furthermore, by exploiting the high spatial resolution of deterministic meteorological models, the information will be extended to all locations without the need to perform downscaling operations at the meteorological station level.