An occupational hygiene investigation of exposure to acrylamide and the role for urinary S-carboxyethyl-cysteine (CEC) as a biological marker

Abstract

Acrylamide has a range of toxicological hazards including neurotoxicity and reproductive toxicity; however, occupational risk management is driven by its genotoxic and carcinogenic potential (it is classified within the EU as a Category 2 carcinogen, R45 and Category 2 mutagen, R46). Since there is the potential for skin absorption and systemic toxicity, biological monitoring may be a useful aid for the assessment of exposure via inhalation, ingestion and dermal absorption. However, there are currently no biological monitoring guidance values (BMGVs). This study describes an extensive survey of potential workplace exposure to acrylamide at the Ciba (Bradford) site to gather data suitable for a BMGV. This manufacturing site is typical within the industry as a whole and includes a cross section of activities and tasks representative of acrylamide exposure. Acrylamide is used in the manufacture of polyacrylamide based products for applications in water treatment; oil and mineral extraction; paper, paint and textile processes. Workers (62 plus 6 controls) with varying potential exposures provided a total of 275 pre shift and 247 post-shift urine samples along with 260 personal air samples. A small non-exposed control group was similarly monitored. Urine samples were analysed for S-carboxyethyl-cysteine (CEC). Airborne, surface and glove samples were analysed for acrylamide. Inhalation exposures were well controlled with values consistently below one-tenth of the UK Workplace Exposure Limit. Engineering controls, personal protective equipment and work practice, all contributed to good control of occupational exposure. CEC was found in urine samples from both exposed workers and non-occupationally exposed controls. At the low levels of exposure found, smoking made a significant contribution to urinary CEC levels. Nevertheless a correlation between urinary CEC and airborne acrylamide was found. A mixed effects model incorporating inhalation concentrations of acrylamide and smoking habits could predict some of the variation in observed post-shift urine results but could be improved through the use of additional surface contamination data. However, the data does not suggest that dermal absorption was a major contributor to the systemic dose. Based on the 90th percentile of the data, inclusive of the effects of smoking and environmental factors, a value of 4 mmol mol(-1) creatinine is proposed as a pragmatic BMGV associated with good occupational hygiene practice and control of workplace exposure. CEC in urine analysis has the utility for routine use as a means to estimate biological uptake where there is a potential for significant exposure or loss of workplace control.