Evaluation of exposure to polycyclic aromatic hydrocarbons in ferrochrome plant workers in South Africa from 2012 to 2015

Abstract

Background: Polycyclic aromatic hydrocarbons (PAHs) are organic compounds that are found in a wide variety of environments. Epidemiological studies have shown excess rates of cancers of the skin, lung, bladder and gastrointestinal tract in some industrial settings where airborne PAH levels are high. Their levels are thus monitored in high-risk workplace environments and in exposed workers. Surrogate markers that are used for monitoring have shown that exposures to PAHs vary among individuals, and in different workplaces. Aims: The study aims to describe the total exposure to PAHs in workers at a ferrochrome plant, the contribution of various sources to overall exposure to PAHs, and analyse trends in urine 1-hydroxypyrene (1-OHP) levels over time (2012-2015). Methods: The investigation was a retrospective record review of PAH monitoring in workers at a ferrochrome plant from 2012 to 2015. The data came from the yearly routine health monitoring of the employees. The study population consisted of men and women who were monitored for exposure to PAHs [coal tar pitch volatiles (CTPV) were measured as benzene soluble matter (BSM) in the air; and in urine (PAHs) as the pyrene metabolite 1-OHP]. A total of 397 records were provided which consisted of records of 111, 102, 83, and 101 employees in the years 2012, 2013, 2014, and 2015 respectively. A total of 86 PAH exposure-related health questionnaires were received. CTPV (air monitoring) data for 2012 to 2015 for 39 employees was also received. Univariate, bivariate, and multivariable analysis was performed on the data. Results: Most of the employees worked in Paste Making (PM) production, PM maintenance, and Safety Health Environment and Quality/ Laboratory (SHEQ/Lab) departments. Most of the employees (>70%) had urine 1-OHP results below the “no-observed-effect-level of iv genotoxic effect” benchmark guideline of 1.4μmol/mol (2012-2015). The median 1-OHP for 2013-2015 was 1μmol/mol, with a similar interquartile range (IQR), but a variation in range over the same years [Range: 2013 (0.1-8.4); 2014 (0.1-4.3); 2015 (0.1-9)]. The personal air monitoring results showed marked variation over the years with the lowest levels recorded in 2013[median (range) 0.00095 (0-0.006)], and the highest levels in 2015 [median (range) 0.0495 (0.015-0.244)]. However, all the personal air monitoring results were below those recommended by the South African regulatory guidelines of 0.14mg/m3. There was a statistically significant relationship between urine 1-OHP and department-section in all the years. However, there was no statistically significant relationship between urine 1-OHP and potential non-occupational exposure to PAHs (e.g. smoking and diet). There was a statistically significant increase in the results for 1-OHP every year from 2012-2015. The increase was still apparent after adjusting for department-sections. The department-sections that had urine 1-OHP levels that were significantly higher than SHEQ/Lab were: furnaces C; furnace D/E; and PM production, in decreasing order respectively. Conclusion: The findings of this research indicate that the PAHs (as CTPV) in personal air within this work environment are controlled at levels below those recommended by the South African regulatory guideline of 0.14mg/m3. The results of urine 1-OHP vary over time and with a combination of work department and section. The department-sections that have urine 1-OHP results that are statistically significantly higher than SHEQ/Lab are: furnace C; furnace D/E; and PM production, in decreasing order respectively. Urine 1-OHP levels, however, are not influenced by personal exposures outside the workplace such as: smoking, diet, heating, cooking facilities and ventilation at home. The regular monitoring of PAHs is necessary in a ferrochrome plant.