Heat Stress among Steel Workers in Al Jubail, Saudi Arabia

Background: Workers working in the steel industry has commonly exposed to heat which lead to health risk. The objective of this study was to assess heat stress among steel production workers. Materials and Methods: It is a cross sectional study, 186 workers were selected through simple random sampling. There are two groups of workers staff and line production. The Wet Bulb Global Temperature (WBGT) index was measured from Heat Stress Monitor (Casella Micro herm WBGT) and Heat Strain Score Index (HSSI). Spearmen correlation for determine the correlation between WBGT and HSSI and association between risk factors and HSSI determined through logistic regression. Results: The mean and SD values of the wet bulb global temperature was 32.46 (2.01) and these values exceed Threshold Limit Values (TLV by American Conference of Governmental Industrial Hygienists (ACGIH) standard and HSSI scores showed that 24.3% of the exposed workers were in red dangerous zone (severe heat strain). The WBGT and HSSI values are positively correlated (r = 0.85) (P = 0.001). Risk factors associated with heat stress after adjustment are age 19-35 years (OR 6.07, CI 1.78-21.90), years of experience >10 years (OR 4.67. CI 1.23-18.42), ever smoking (OR 1.58, CI 1.08-4.57) and overweight (OR 1.56, CI 1.20-12.48). Conclusion: The finding of this study showed that heat stress is common hazard among steel workers and the heat conservation planning intervention action should be conducted to reduce exposure.


Introduction
Heat is considered as one of the most hazardous physical agents that can cause multiple health problems in the workplace 1 . Abnormal working environment might create negative consequences both on workers' health and productivity. Long term occupational exposure to heat which can results in heat related disorders, such as dehydration, rash, fatigue, cramps, syncope, and heatstroke 2,3 .
Steel industry workers exposed to many hazards and heat stress one of the common hazards 4 . They are exposed to a high temperature exposure during the various processes of steel manufacturing such as extraction, tapping, burning a scrap, casting and molten 4 . High temperature caused various health effects such as fatigue, lethargy, dizziness, heat rashes, unstable movement and heat collapse 5 .
Result of the previous study found that workers working in the steel industry exposed to heat which lead to heat stress and WBGT values from 31 to 33°C 6 . In the previous study found that human body thermal sensation has high sensitivity during high temperature and advised to reschedule their activity to prevent thermal shock 7 . Eye dryness was common among workers in steel industry 8 .
Saudi Arabia (SA) is one of the hottest countries in the world and eastern region where many industrial units are working and there are many steel industries in this region 9 . During high temperature various health hazard on the human body and various health disorders were found among workers in this high temperature 10,11 . Industrial workers in steel company are frequently exposed to severe heat stress during their duty, which may strongly decrease work efficiency and affect their health and survival 12 . In the best of our knowledge there is no previous study conducted in eastern region of Saudi Arabia to determine the heat stress among steel workers. This study will help to identify the factors which contribute to heat stress among steel workers and determine the prevalence of street stress among steel workers. Research objective of this study is to assess the heat stress among steel workers in Jubail, KSA. Vol 20 (1&2) | January-June 2020 | http://www.informaticsjournals.com/index.php/JEOH/index Nofal Falah Alshammary, Khaled F. Salama and Mubashir Zafar

Study Setting, Study Design and Inclusion and Exclusion Criteria
The study was conducted in a steel industry located in a Jubail city. Study subjects represents as a total of n = 186 including administration employee n = 79 and line production workers n = 107. It's a cross-sectional study and eligibility for inclusion of study as line production workers exposed to heat during their working, the administrative workers were not exposed to heat and excludes those workers who works as maintenance and workshop warders that not regularly exposed to heat.

Sample Size, Data Collection Tool Study Variables
A sample size was calculating from EPI info calculator. Total 186 steel workers is needed to detect an odds ratio of 4, assuming heat related illness of 76% in group WBGT below TLV (Threshold Limit Values) with a power of 80% and the significance level at 5%.

WBGT
In the steel factory work environment, Wet Bulb Globe Temperature (WBGT) index were used to assessment heat stress. Wet Bulb Globe Temperature included dry bulb (air) Temperature (Tdb), natural wet bulb Temperature (Tnwb) and globe Temperature (Tg). The formula of WBGT in solar radiation (outdoor) is = 0.7 × Tnwb + 0.2 × Tg + 0.1 × Tdb and in indoor is = 0.7 × Tnwb + 0.3 Tg.
The Study instruments was used (Quest Technologies, WI, USA) it included sensors which measure relative humidity (RH), Tg and Tdb. Validation of these instruments to measure and record WBGT according to ISO 7243 standards 14 . The observed values of WBGT in the steel mill plant practice 75% work and 25% rest in work-rest regimen scales according to ACGIH standards.
Self-administrated reliable and validated Heat Strain Score Index (HSSI) questionnaire was distributed among steel workers (n = 186) to collect data from worker and analyze Heat Strain score Index. The questionnaire was included demographic data (Age, nationality…etc.), years of experience, level of education, smoking, workload and all other variables. The HSSI scale includes 17 items, observation and questions relating to heat stress were also included. There are three levels of risk, no heat strain (score less than 13.5), the low heat strain (13.6 to 18) and high heat strain (>18.1).

Ethical Approval
Study protocol was approved from the Institutional Ethical and Review Board (IRB) of IAU. Informed written consent was obtained before the start the data collection.

Statistically Analysis
Study data analyzed by using the Statistical Package for Social Sciences (SPSS) version IBM 24. The characteristics of the steel workers are described using means, standard deviation and proportion were calculated. Chi-square test used to compare the proportions between the groups. Multinominal tegression analysis was used for studying the impact of heat stress and other related variables on the heat disorder illness among steel workers. A p-value <0.05 will be considered statistically significant.

Results
Mean age of study participants (line production and administrative) are of 33.66 (SD±6.82), and 38.32 (±9.52), respectively. The characteristics of administrative and line production employee difference are age, nationality, working hours and daily shift, these differences were statistically difference (p-value <0.05) ( Table 1).
The prevalence of heat stress is 14% who were in the red zone (danger level), 12.4% of the respondents were in the yellow zone (alarm level) ( Table 2).
The prevalence of the heat stress among the two groups of the study participant are 2.5% of the administration staff were in the yellow area compared to 19.6% of the line production staff. Only 24.3% of the line production staff was in red zone (Table 3). There is positive correlation of WGBT and HSSI (Table 6).

Discussion
This study found the high prevalence of heat stress among steel workers specifically line production workers. There are various factors which contributed to heat stress.
The results of the present study revealed that most of the steel workers in the current study were in the green zone (save level), this was followed by who were in the red zone (danger level). The result of this study is in consistence with past study where the HSSI values were in red zone among production workers. 98.62% of the workers are in red zone and 1.38% in yellow zone 13 . In the present study, the average WBGT record among line production workers and administrative employees were 27.5 and 37.40 respectively. WBGT in this study shows positive correlation with heat stress. In Dehghan, et al. study on workers in Hot/Humid working conditions (WBGT>30°C), the heart rate of subjects was increased and the overweight workers was showed cardiac strain higher in compared with that in normal weight workers which is same with the findings of the present study 14 .
The study of Peiffer and Abbiss conducted on miners working in an iron ore mine in northwest of Australia and the results showed that deep body temperature of the workers was higher at the end of shift work (37.6°C) than in the beginning of the shift work (37ºC) 15 . The study by Falahati, et al., the result found that there was a significant correlation between heath indices with deep body temperature. Moreover, WBGT was the most accurate index for estimating heat stress in employees 16 .
The result of this study showed that the level of heat stress indices was higher in work state. The maximum WBGT values recorded in this study is 30.76ºC which is higher compared to ISO 7243 recommended limits (<30ºC). The result is consistent with the other study 17 . In another study, workers experienced had positive correlation between WBGT and aural temperature 18 .
In previous study 19 , determined the relationship of heat stress and thermal hazard in a steel mill. They found that workers employed in the steel industry are exposed to heat stress and heat protection methods should be carried out for workers. This result was same with this study. In the present study, overweight subjects were 1.7 times at risk of heat stress with OR (95% CI) at 1.7 (1. 16-17.24).
Overweight participants had high heat stress due to physiological and thermal response. Moreover, Tuomaala et al. determine correlation between HSSI and BMI >25. Result showed that no relationship. These result not in line with this study 20 .

Conclusion
Steel workers have high level of heal stress with WBGT positive association with physiological parameters. It is recommended with HSSI screening with WBGT preventive measure for continuous monitoring heat stresses among exposed workers. Collaborated action is required to mitigate the effects of occupational heat strain.