Benzo[a]pyrene, a famous chemical of the Polycyclic Aromatic Hydrocarbons (PAHs) family, is an omnipresent environmental pollutant which is considered as carcinogenic. At LIH’s Department of Population Health, the Human Biomonitoring Research Unit has identified four new metabolites of this compound that can be detected and precisely quantified in hair, and thus serve as potential new biomarkers for the assessment of human exposure to benzo[a]pyrene.

PAHs and their derivatives are produced by incomplete combustion of organic matter (e.g. fossil fuel combustion, coal tar, vehicle exhausts, cigarette smoke, grilled food). Workers in road asphalt paving and steel production are especially exposed to these harmful compounds. Since exposure to PAHs is suspected to be responsible for severe health issues such as cancer, cardiovascular diseases and neurological disorders, significant research efforts go into the development of efficient strategies for the assessment of human exposure to these ubiquitous pollutants.

Classically, the analysis of hydroxylated PAHs in urine is used to assess human exposure to PAHs. The Human Biomonitoring Research Unit has proven in multiple studies that hair is a reliable biomonitoring matrix to assess long-term exposure to different types of pollutants. In this context, Dr Nathalie Grova seeks to study whether exposure to PAHs can be measured in hair samples. ‘In previous work that we carried out in 2013, we were able to measure 20 monohydroxylated PAHs in hair representative of 13 parent compounds’, says Dr Grova. ‘This time we focused on four tetrahydroxylated metabolites of benzo[a]pyrene which could constitute suitable biomarkers for the assessment of benzo[a]pyrene exposure as they allow quantitative evaluation of the internal dose, appear more relevant than mono-hydroxylated forms for the measurement of the heaviest compounds of the PAH family, and supply information about the toxicity of the parent compound linked to individuals’ specific metabolism’, she explains.

The group therefore developed a new analytical method based on gas chromatography-tandem mass spectrometry to measure their concentration in hairs collected from rats under controlled exposure to PAHs as well as from 16 human volunteers. ‘We succeeded in detecting precisely even very low concentrations of the four tetrahydroxylated metabolites and observed that there was a linear correlation between dose of exposure and concentration levels in hair. There was also a significant correlation between one of the four metabolites in hair and the number of DNA adducts, showing the ability to predict DNA alterations by benzo[a]pyrene’, Dr Grova explains. ‘The detection method was sufficiently sensitive to monitor environmental levels of exposure and to distinguish between smokers and non-smokers among the human volunteers. It would be interesting to extend this study to a larger sample size including both exposed workers and general population’, she says.

‘This is the first time that tetrahydroxylated metabolites of benzo[a]pyrene have been detected in hair samples’, emphasises Dr Brice Appenzeller, Head of Human Biomonitoring Research Unit. ‘These biomarkers are complementary to those that we already identified and could serve to monitor long-term and multi-exposure to PAHs’, he adds.

The results of this study were published in frontline in the journal of “Analytical and Bioanalytical Chemistry” in February 2016.

Link to online abstract: http://link.springer.com/article/10.1007%2Fs00216-016-9338-x