Analyzing the Risk of Safety Accidents: The Relative Risks of Migrant Workers in Construction Industry

: This study analyzed the relative risks of migrant workers, and identiﬁed risk factors based on quantitative data for the systematic safety management of migrant workers. Many studies have found that migrant workers are more vulnerable to safety accidents than non-migrant workers. Nevertheless, there are few quantitative studies of migrant workers’ accident-risk in the construction industry, where safety accidents are most frequent. In addition, safety management for the identiﬁed accident risk factors has not been implemented systematically. To ﬁll the gap, this study uses safety accident data from construction sites, from the + , for the methodical safety management of migrant workers. The t-test and multiple regression analysis methods are used to deﬁne the variance in non-migrant and migrant workers, and the risk indicators, respectively. The two analyses show that the results for migrant construction workers were 2.2% higher in safety accident severity than non-migrant workers, and signiﬁcant factors are also di ﬀ erent. This study’s results will provide critical guidance for the safety management of migrant construction workers.


Occupational Safety of Migrant Workers
As the difference in the economic conditions between countries expands, the numbers of migrant workers are increasing worldwide because of differences in wage levels and labor shortages. These migrant workers are being investigated as among the most vulnerable members of migrant society [1,2]. Past research has revealed several reasons why migrant workers are vulnerable. First, there are cultural and language barriers. According to Son et al. (2013), migrant workers have different languages and cultures to the locals [3]. This lack of common understanding tends to increase their risk of accidents over that of non-migrant workers [4,5]. In addition, the lack of communication among migrant workers, which is due to the lack of language skills in migrant areas, makes them vulnerable to safety accidents [6,7]. Furthermore, differences in cultural backgrounds are essential considerations for the safety of construction sites, beyond language barriers. Lack of knowledge in cultural differences can affect communication on construction sites in a manner similar to language barriers. That is, cultural differences, e.g., uncertainty avoidance, power distance and collectivism, have a detrimental effect on construction site safety. The reason is that cultural differences act as a barrier to communication between migrant workers and supervisors on construction sites, which adversely affects the safety of construction sites [8,9]. Second, there is a lack of safety education. Cheng et al. (2013) found that migrant workers are vulnerable to safety accidents because of inadequate safety and health education [10]. This is one of the main causes of industrial accidents, and only a

Status of Industrial Accidents among Korean Construction Workers
In 2018, the number of casualties increased by 1768 (7.15%) in the construction industry, compared with the previous year, and the total number of industrial accidents in the construction industry was the second highest in 2018, at 6486 (29.16%). The major causes of accidents in the construction industry were collapse, pinching, crushing, hitting objects, flipping and bumping, accounting for 8741 (31.57%) out of the total 27,686 accidents. The highest level of death in the in the distribution map of deaths by industry was in the construction industry, at 26.61% [29].

Status of Safety Management in the Construction Industry in Korea
When comparing the industrial accident rate and death fatality rate in 2017, it was found that Korea's industrial accident rate was 0.84%, which was lower than the UK and the US, at 2.62% and 3.04%, respectively. However, Korea had a relatively higher death toll at 1.9% , compared to 0.16% in the UK and 0.95% in the US [29]. In other words, the industrial accident rate in Korea appeared to conflict with the disaster distribution of the Heinrich Pyramid, where the incidence rate increased in the order of serious, minor, and injury-causing accidents. The reason for this phenomenon is that many accidents are covered up, so they are not reported properly. To prevent safety accidents, analysis through accurate data collection is necessary.
The accident rate and death rates in the construction industry in 2017 were 0.84% and 1.90% , respectively, compared with 0.48% and 1.05% in the domestic industry, respectively, the construction industry's rates being 1.75 times and 1.81 times higher, thereby making it the most dangerous industry.
One reason for this is that more high-rise buildings are being constructed, and the number of deaths and permanent obstacles in high-rise buildings is high, resulting in higher accident rates compared with other industries [30]. Owing to the nature of construction work, many work activities are performed outside. Consequently, there is a high risk of accidents due to heavy work in the hot sun or rain. In addition, heavy work, including that involving roofs, ladders and scaffolding, increases the risk of accidents. Moreover, the use of hazardous machinery, equipment, tools and heavy materials increases the risks to workers' safety and health [31].
To prevent industrial accidents, the Ministry of Employment and Labor and the Safety and Health Agency have been compulsorily conducting basic safety and health education for construction workers since 2012. However, to date, there has been no significant change in the industrial accident rate. In the current construction occupational safety and health system, safety management cost estimate standards and safety manager appointment systems are in place to prevent industrial accidents. Because the costs and manpower are set according to the size of the construction cost at the site, the system is inevitably vulnerable to inadequate safety accidents prevention at sites where the construction cost is low. In addition, the safety management cost is calculated by multiplying the construction cost by a certain rate and the successful bid rate, so many cases do not reflect the site's specificity.

Migrant Workers in the Construction Industry
There is a shortage of new manpower, and the existing manpower in the Korean construction industry is aging. This gap is filled with an influx of migrant workers. In particular, in the case of civil works on sites in mountainous and remote areas, the manpower shortage is getting worse. Thus, the influx of migrant workers is essential [32]. The total quantity of migrant workers in 2017 was 10.1% of all construction workers; by industry type, this is 29.0% of civil engineering, 62.3% of construction, and 8.8% of plant work. By job category, the proportion of migrant workers was high in all jobs except welders. In particular, it was found that many foreigners flowed in for so-called hard work and low-wage work, such as steelwork and rebar [32].
Consequently, as seen in many previous studies, the construction industry has higher safety accident and mortality rates than other industries. Furthermore, migrant workers in the construction industry (migrant workers are generally more vulnerable than non-immigrant workers) are the most vulnerable working class.
The New Oxford American Dictionary has defined the word "culture" as the "customs, arts, social institutions, and achievements of a particular nation, people, or other social group," in other words, "the attitudes and behavior characteristic of a particular social group" [33]. Culture is also defined as "the set of attitudes, values, beliefs, and behaviors shared by a group of people, communicated from one generation to the next" [34]. The common sentiment of such various definitions is that culture is what is shared within certain social groups, and it has great influence on how one communicates with others.
Recent construction sites in Korea have witnessed and experienced the significance of the term, and concept, of culture. That is, a number of construction sites in Korea are now hiring workers of a variety of backgrounds, in terms of languages, nationalities and culture. Consequently, for the construction sites in Korea, in which a variety of cultures in the employment setting [35] exist, strategies that embrace such diversity in culture and background are strongly called for, in order to establish more productive and efficient workforce management [36].
Cultural differences can lead to a decline in productivity and efficiency. Furthermore, national cultural diversity causes low morale, low quality of work, workplace conflict, and stress-related illnesses [37]. Previous studies have commonly pointed out such unsafe conditions, unsafe behaviors, and unsafe task methods or sequencing as the cause of safety accidents. [38][39][40]. In these circumstances, project managers need to be knowledgeable and skilled regarding diversity management, in order to effectively lead their multi-cultural workforce and to prevent safety accidents.

Aim and Framework of the Study
The previous papers and statistics have shown that migrant workers are more vulnerable to safety accidents than non-migrant workers. Nevertheless, there are few quantitative studies on the risk of accidents among migrant workers in the construction industry, where safety accidents are most frequent. In addition, safety management based on accident risk factors has not been implemented systematically. In order to mitigate the differences between migrant workers and non-immigrant workers, there is a desperate need to accommodate them through the improvement and development of new safety management strategies and tools. In the absence of these new strategies and tools, it is difficult to overcome problems such as delays in construction due to safety accidents, excess safety budgets, and high mortality rates. Consequently, the ultimate goal of the study is to provide a better understanding of construction safety management through the development of risk factors that can affect the safety of construction sites for migrant workers. Accordingly, this study analyzes the relative risks of migrant workers residing in Korea and identifies risk factors, based on quantitative data, for the systematic safety management of migrant workers. To achieve this study's goal, the following procedures were conducted. First, safety accident data from construction sites were collected from the Korea Occupational Safety and Health Agency (KOSHA). Second, the difference between the safety accident risk of non-immigrant workers and that of migrant workers was statistically proven using the t-test. Third, by using multiple regression analysis, the significant factors affecting migrant construction workers and safety accidents were examined.

Data Collection
This study used data from Korea Occupational Safety and Health Agency (KOSHA)'s accidental injuries (excluding deaths) at construction sites in Korea from 10 years, between 2010 and 2019. KOSHA is a quasi-government agency under the Ministry of Employment and Labor, established in 1987 under the Korea Occupational Safety and Health Agency Act, enabling workers to work safely and healthily, and helping employers prevent accidents. Its main tasks are related to industrial safety, such as research and development, distribution of industrial accident prevention technologies, and occupational safety and health training. The data comprise accident details, such as the construction progress rate at the time of the accident, construction scale, accident type, nationality of the victim of the accident, date and time of the accident, number of days of treatment for the accident, day of the accident, time of the accident, site address and accident summary. The number of treatment days was used as a dependent variable to quantify the severity of accidental injuries.

T-Test
This study used the t-test to analyze the dissimilarities between the two categories, i.e., non-migrant and migrant workers. If there are differences between the two categories in the days of treatment, it would be possible to account logically for the difference in risk management and risk, between non-migrant and migrant workers, when carrying out construction management on future construction sites. Table 1 shows the t-test results. The p-value of 0.014 is smaller than 0.05, which verifies that the days of treatment for non-migrant and migrant workers are significantly different. The mean value signifies that migrant workers have 2.2% more treatment days than non-migrant workers.

Multiple Regression Analysis
This study adopted a multiple regression analysis to describe the relationship between the dependent variable (days of treatments) and independent variables. The variables are listed as shown in Table 2. The dependent variable is the days of treatment, which is the number of days, including the total number of medication days, listed in the medical billing statement, to quantify accident severity. The progress rate represents the construction site's progress rate at the time of an accident; the accepted progress rate reflects the degree of risk of the construction project. Many studies found that the progress rate and the risk amount have a significant relationship, since the progress rate increases as the complexity of the construction project and risk amount increase [41,42].
The construction scale by construction amount is based on the Korea Occupational Safety and Health Act. It is a well-known indicator of the risk amount because the risk and building scale have a statistically significant association [43,44]. Furthermore, small-medium construction sites are relatively vulnerable to accidents [45]. In this study, according to the construction scale prescribed by the Korea Occupational Safety and Health Act, more than KRW 12 billion won was defined as a large-scale construction site, and less than KRW 12 billion won as a small-or medium-sized construction site.
The classification of occupations is based on the Korean standard. The occupational classification, according to the Korean Standard Occupational Classification, is for classifying and counting occupational information obtained through employment-related statistical surveys, such as economically active population surveys, population and housing surveys, regional employment surveys, and various administrative data. In addition, it aims to characterize hazards in the health field according to the job, and provide guidelines for comprehensive management of similar jobs [46]. To ensure the consistency and comparability of statistical data, the International Labor Organization's International Standard Classification of Occupations was established to internationally compare and use domestic statistics from various types of job information, and thus, it was applied to the risk assessment of construction workers.
The variables, day of the week, and accident time are adopted to show the risks associated with the construction site's working conditions. Construction workers are exposed to direct risks depending on the working environments at the construction site. Construction work is characterized by continuously changing work content and intensity, by time or day of the week. Therefore, identifying the time and day of the week when accidents occur most often is helpful for preventing accidents [47,48]. For example, construction safety accidents occur during work-intensive hours, which are concentrated in the middle of the morning and early in the afternoon. Therefore, it can be said that the accident incidence rate is high in a period with a large amount of work, but the difference in the incidence rate, according to task difficulty by period, can be represented. Therefore, in this study, the time zone was divided into four units (morning, afternoon, evening and night, and dawn), which were, along with the day of the week, used as variables.
The employment is divided into two groups, i.e., regular workers and irregular workers. Migrant workers have less regular employment contracts than non-migrant workers, which has a negative impact on migrant workers [2,28]. According to a study by Lim (2015), approximately 89.5% of workers in the construction industry were irregular workers, with less than six months of experience. Owing to the nature of the construction industry, it is necessary to move the site on a team-by-team basis, and the head of the workgroup tends to consider the construction schedule to be more important than safety. Moreover, the shorter the construction period, the more workers move, the less safety management supervision, and the higher the number of safety accidents among non-regular construction workers [49]. Thus, employment patterns can also be a significant indicator of safety accident risk. Descriptive statistics of the independent variables and dependent variable are presented in Table 3.  Table 4 shows the regression analysis summary. The dependent variable, days of treatment, is transformed by a natural log. The non-migrant worker's model is statistically significant (F-value > 1). The adjusted R-square value of 0.314 denotes that this relationship is clarified with a 31.4% margin of variance. The migrant's model is statistically significant since the p-value is less than 0.05. The adjusted R-square value of 0.392 designates that this relationship is explained with a 39.2% margin of variance. In the non-migrant worker's model, there are five significant variables: progress rate, cost of construction, classification of occupations, accident time, and employment. The day of the week is disqualified because the p-value is higher than 0.10. The Variance Inflation Factors (VIF) values range from 1.000 to 1.050. The VIF values signify that the variables have no critical multicollinearity. In the migrant worker's model, there is a significant variable: the day of the week. The other variables are excluded because the p-value is higher than 0.10. The VIF values range from 1.034 to 1.230. The VIF values illustrate that the variables have no serious multicollinearity.

Discussion
This study examined the relative risks of migrant workers in the construction industry in Korea, and defined risk factors, based on quantitative data, for the methodical safety management of migrant workers.
The t-test verifies that the days of treatment for non-migrant and migrant workers in the construction site are significantly different. The days of treatment statistic for migrant workers is 2.2% higher than the days of non-treatment statistic for migrant workers. This reinforces previous studies' conclusions that migrant workers at construction sites are more likely to suffer from safety accidents than non-migrant workers. This reinforces the previous studies' conclusions that migrant workers on construction sites are more likely to suffer from safety accidents than non-migrant workers [29][30][31][32]. Consequently, it is necessary to consider the relative risk to migrant workers for safety management at the construction site; furthermore, it is necessary to focus on migrant workers to reduce safety accidents.
The multiple regression analysis was conducted to identify the significant indicators among the independent variables. The models are statistically significant, which proves that the days of the treatment can be estimated by the independent variables. Safety accidents, and significant variables of non-migrant workers and migrant workers, were dissimilar. There are five important variables in the non-migrant worker model: progress rate, cost of construction, classification of occupations, accident time and employment. Conversely, the day of the week is the only important variable in the migrant worker's model. Migrant workers were found to be affected by safety accidents depending on their concentration and difficulty in understanding safety education. Thus, migrant workers need additional safety education and policies according to their experience and skill levels. In addition, this study provides further evidence that construction workers are exposed to direct risks depending on the working environment, i.e., day of the week, of the construction site [47,48]. The results of this study can be used by construction supervisors to develop strategies and tools for preventing accidents and reducing accident risk among migrant workers. In addition, the results of this study have real-world and theoretical implications, for the better understanding and improvement of construction safety and migrant construction workers.
Moreover, this shows that the two groups have different characteristics and need different forms of management as regards safety accidents. Consequently, significant indicators are not only an essential source of safety management for non-migrant and migrant workers in Korea, but also show that a different approach is needed for the two groups. For example, to reduce the occurrence of safety accidents for migrant workers, it is important to improve their working environments and prevent risk factors. However, it is also important to reduce the occurrence of safety accidents by providing adequate information, and understanding migrant workers' characteristics. This is because the provision of, and familiarity with, safety and health information can be more important for non-migrant workers, who have difficulties in fully understanding the safety and health information because of differences in language and culture [50]. As a way to solve this problem, Occupational Safety and Health Administration (OSHA) in the US has achieved great results by supporting coordinators for workers with diverse backgrounds working in small businesses, as well as for local unions, and other non-English-speaking workers who have difficulty communicating in Spanish or English [51]. In this manner, for the safety management of migrant workers, special government-wide safety management policies are needed.
Furthermore, to reduce the safety risk to migrant workers, it is necessary to combine technologies, such as big data, AI (Artificial Intelligence), IoT (Internet of Things), and ICT (Information & Communication Technology).
In the case of migrant workers, safety accident data can be concealed and manipulated owing to their disadvantaged status. To prevent this, it is essential to develop a system that can systematically collect transparent safety accident data. In addition, based on systematically collected data, it is necessary to establish an integrated safety management system that predicts and prevents an environment in which an accident may occur, or calculates the likelihood of an accident that fits the characteristics of a construction site. Finally, it is essential to create a safety climate of a new paradigm by managing the process of sharing and implementing decisions related to safety management made by the fourth industrial revolution.

Conclusions
Many previous studies have found that migrant workers are more vulnerable to safety accidents than non-migrant workers, but there have been few quantitative safety accident risk studies for migrant workers in the construction industry, where safety accidents are most frequent. Thus, to meet the demand, this study quantitatively analyzed the accident risks for migrant workers in the construction industry in Korea, where industrial accidents occur most, and investigated the factors affecting the risks of migrant workers. Through statistical analyses, factors affecting safety accidents of migrant workers were identified, and a method for effective safety management was proposed. These results constitute important reference materials for the safety management of migrant workers in construction companies, client organizations or contracts, and safety-related government agencies.
This study selected its scope to reflect the recent changes in construction sites in Korea, in which many migrant workers, not only Koreans, with a variety of backgrounds, in terms of languages, nationalities and cultures, are found. More specifically, this study looked into the safety management of migrant workers, mainly from Southwest Asia and China. Therefore, in Korea and in countries with similar construction environments, the methodology and indicators developed in this study can be used to develop safety management strategies and tools for accommodating migrant construction workers. However, to apply the methodology from this study to other studies with different settings, e.g., different populations, environments of construction sites and cultures, additional research and verification is required, as the composition of the same variables can produce different results in other cultures. For example, fasting during the day in Ramadan had to be taken into account, as it could affect the worker's physical condition [52]. Further, it is indicated that the siesta in Spanish culture can affect the workers' performance [53]. In addition, in order to strengthen the results of this study in the future, verification through accident data from other countries is also necessary. Another point to consider for more quantitatively systematic and robust studies in the future is that, because only the data of one KOSHA agency was collected and analyzed in this study, more in-depth analyses are needed, necessitating the collection of various data, such as data of longer period and/or from more sources, which is provided by several insurance companies or government agencies.