[Published] Statistical modeling of occupational exposure to polycyclic aromatic hydrocarbons using
Occupational exposure to contaminants is ubiquitous, even if we are not aware of it. Monitoring systems like the US Occupational Safety & Health Administration's Integrated Management Information System is one such system that has provided a wealth of information when it comes to looking at risks of exposures on the job. In 2011 I had the opportunity and privilege to work with Dr. Jérôme Lavoué and Dr. Igor Burstyn to explore what we can do with these monitoring systems with respect to a group of chemicals called polycyclic aromatic hydrocarbons. If you have recently ate a steak that had some black, grill marks, congratulations, you've been exposed*.
Abstract: Polycyclic aromatic hydrocarbons (PAHs) are a group of pollutants with multiple variants classified as carcinogenic. The Occupational Safety and Health Administration (OSHA) provided access to two PAH exposure databanks of United States workplace compliance testing data collected between 1979 and 2010. Mixed-effects logistic models were used to predict the exceedance fraction (EF), i.e. the probability of exceeding OSHA's Permissible Exposure Limit (PEL = 0.2 mg/m3) for PAHs based on industry and occupation. Measurements of coal tar pitch volatiles were used as a surrogate for PAHs. Time, databank, occupation, and industry were included as fixed-effects while an identifier for the compliance inspector was included as a random effect. Analyses involved 2,509 full-shift personal measurements. Results showed that the majority of industries had an estimated EF < 0.5, although several industries, including Standardized Industry Classification codes 1623 (Water, Sewer, Pipeline, and Communication and Powerline Construction), 1711 (Plumbing, Heating, and Air-Conditioning), 2824 (Manmade Organic Fibres), 3496 (Misc. Fabricated Wire products), and 5812 (Eating Places), and Major group's 13 (Oil and Gas Extraction) and 30 (Rubber and Miscellaneous Plastic Products), were estimated to have more than an 80% likelihood of exceeding the PEL. There was an inverse temporal trend of exceeding the PEL, with lower risk in most recent years, albeit not statistically significant. Similar results were shown when incorporating occupation, but varied depending on the occupation as the majority of industries predicted at the administrative level, e.g. managers, had an estimated EF < 0.5 while at the minimally skilled/labourer level there was a substantial increase in the estimated EF. These statistical models allow the prediction of PAH exposure risk through individual occupational histories and will be used to create a job-exposure matrix for use in a population-based case-control study exploring PAH exposure and breast cancer risk. [Full Article]
* Disclaimer: The likelihood of PAH from your steak being problematic is low, unless you're eating them quite regularly. For more tidbits about what else will cause cancer, click here.