Seasonal variations in the levels of PAH-DNA adducts in young adults living in Mexico City

Abstract

Polycyclic aromatic hydrocarbons (PAHs) are ubiquitous components of polluted air. The Mexico City Metropolitan Area (MCMA), one of the most densely populated areas in the world, is 2240 m above sea level. At this altitude, less oxygen is available, making combustion less efficient and therefore producing more PAH pollutants. According to the Automatic Monitoring Network in Mexico City (RAMA, for its Spanish initials; http://www.sma.df.gob.mx/simat2/informaciontecnica/index.php?opcion=5&opciondifusion_bd=90), which performs environmental monitoring, the critical air pollutants in Mexico City are ozone and particulate matter (PM). PM emissions increase during the dry season (winter to spring) and decrease during the rainy season (summer to autumn). The bioactivation of some PAHs produces reactive metabolites that bind to DNA, and the presence of elevated levels of PAH-DNA adducts in tissues such as blood lymphocytes represents an elevated risk for the development of cancer. We have compared the levels of PAH-DNA adducts and the percentage of cells with chromosomal aberrations (CWAs) using a matched set of peripheral blood lymphocytes obtained on two separate occasions from young non-smoking inhabitants of the MCMA (n = 92) during the 2006 dry season and the following rainy season. PAH-DNA adducts were analysed using the r7, t8-dihydroxy-t-9, 10-oxy-7,8,9,10-tetrahydrobenzo[a]pyrene (BPDE)-DNA chemiluminescence immunoassay (CIA). The percentages of CWA were determined in cultured lymphocytes from the same individuals. Both DNA adduct levels and chromosomal aberrations were tested for correlation with lifestyle and the polymorphisms of cytochromes P450 CYP1A1 and CYP1B1 as well as glutathione-S-transferases GSTM1 and GSTT1. The levels of PAH-DNA adducts were significantly higher (P < 0.001) in the dry season (10.66 ± 3.05 per 10(9) nt, n = 92) than during the rainy season (9.50 ± 2.85 per 10(9) nt, n = 92) and correlated with the seasonal levels of particulate matter with a diameter of ≤ 10 μm (PM(10)). The percentage of CWA was not seasonally related; however, significant associations between the number of risk alleles and adduct levels in the dry (R = 0.298, P = 0.048) and in the wet seasons (R = 0.473, P = 0.001) were observed.

A review of airborne polycyclic aromatic hydrocarbons (PAHs) and their human health effects

“…Moreover, as PAHs have the potential to interfere with hormone systems, they can exert harmful effects on reproduction and immune function. As such, DNA damage induced by PAH exposure has been demonstrated by numerous authors (Garcia-Suastegui et al, 2011;Gunter et al, 2007;John et al, 2009). Long-term exposure to PAHs is suspected to raise the risks of cell damage via gene mutation and cardiopulmonary mortality (Kuo et al, 2003).…”

Biomarkers of ambient air pollution and lung cancer: a systematic review

“…As illustrated in figure 4, some studies found a higher frequency of CAs with exposure to heavy air pollution,50–56 others did not find statistically significant associations57 58 and others produced contradictory results 59…”

DNA adducts and combinations of multiple lung cancer at‐risk alleles in environmentally exposed and smoking subjects

“…A significant relationship was found in long‐term cigarette smokers (28 ± 18 cigarettes per day for at least 40 years) who carry multiple at‐risk alleles. García‐Suástegui et al [] evaluated the levels of DNA damage in a population resident in Mexico City, Mexico, and a panel of at‐risk alleles of genes from activation and detoxification pathways. The levels of DNA adducts were significantly linked to the “sum of at‐risk alleles” in individuals heavily exposed to air pollutants.…”