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A broad sector of the brick industry in Mexico is carry out by informal small groups using traditional brick kilns installed in the backyard of their homes. The lack of technology and the use of cheap fuels contributes importantly to the air, soil and water pollution. The incomplete burning of organic fuels and mud produces polycyclic aromatic hydrocarbons (PAHs), considered highly toxic for human. However, epigenetic effects linked to hydrocarbons aromatic polycyclic exposure are still poorly studied. In this study DNA methylation patterns were analyzed in relation to PAHs exposure.
Methods
A cross-sectional study was carried out in a group of brick manufacturer men in San Luis Potosi, Mexico. Smoking and drinking habits, clinical history, working time as well as socioeconomic characteristics were compiled by participants through a questionnaire. 1-HOP was determined from urine by High-performance liquid chromatography while genomic DNA was isolated from a blood sample for methylation analysis by pyrosequencing. Associations between urinary 1-HOP levels and global/specific DNA methylation were evaluated using multivariate regression models.
Results
Median 1-HOP levels were 0.18 microg/g creatinine (range 0.02-1.11) when a single sampling was conducted in the winter period. After adjusting for potential confounders, 1-HOP urine concentrations were associated with DNA methylation in interleukin 12 gene promoter (Beta -1.57; 95% CI -2.88 to -0-25; p 0.02) while a marginal association was found for TNFalpha gene (Beta -1.76; 95% CI -8.6 to 0.62; p 0.08) and ALU sequences ( Beta -1.59; 95% CI -1.28 to 0.15; p 0.1).
Discussion
Although urinary 1-HOP concentrations were bellow the occupational exposure guidelines, a tendential change on specific and global DNA methylation induced by PAHs even at relatively low exposure was observed. This work is the first report of occupational risk assessment in the brick manufacturing industry using epigenetic biomarkers. Larger sample size are needed for further studies.