Exposure levels of Polycyclic Aromatic Hydrocarbons in Mexico City

E. Salinas-Talavera (1), V. Mugica-Alvarez (1), B. Valle-Hernández (1), A. de Vizcaya-Ruiz (2), A. Eiguren-Fernández (3)

1 Universidad Autónoma Metropolitana-Azcapotzalco, Mexico D.F. 2 Centro de Investigación y de Estudios Avanzados-I.P.N., México D.F., Mexico. 3 Southern California Particle Center and Supersite, Institute of the Environment, University of California L.A.

     Abstract Number: 366
     Last modified: November 9, 2009

Abstract
The 16 US-EPA priority polycyclic aromatic hydrocarbons (PAHs), were determined in PM$_(10) and PM$_(2.5) during three seasons in the North of Mexico City, where the most important industrial area is located, in order to determine the exposure levels of the inhabitants of that area. PAH measurements in both particle sizes presented significant seasonal variation showing the greatest concentrations in the dry-cold season (October-January), with levels of PAHs up to 3 times larger than in the dry-warm (February-May) and rainy (June-September) seasons. Average concentrations of the sum of the total measured PAH in PM$_(10) were 17, 16 and 26 $^(-3) for dry-warm, rainy and dry-cold seasons respectively, whereas for PM$_(2.5) the sum was 14, 14 and 20$^(-3) respectively. The levels of the seven PAH considered as possible or probable carcinogenic (benzo[a]anthracene, chrysene, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, indeno[1,2,3, c-d]pyrene, and dibenzo[a,h]anthracene) represented 69 and 67% of the PAH contained in PM$_(10) and PM$_(2.5) respectively. Considering the EPA assumption that an individual breaths 20 m$^3 a day, the calculated medians of daily intake of carcinogenic PAHs due to air pollution for each season for PM$_(10) and PM$_(2.5) were 193 and 165 ngday$^(-1) (dry-warm), 183 and 160 ngday$^(-1) (rainy), and 295 and 226 ngday$^(-1). These values are higher than the median value of 160 ngday$^(-1) estimated by Menzie et al in 1992, as a daily potential dose of carcinogenic PAHs.
Benzo[a]pyrene (BAP) has been considered the most important index for the whole PAHs carcinogenicity and the European Union has proposed an annual standard of 1 ngm$^(-3) of BAPeq in particles to be achieved in 2010 with the aim to protect the population’s health. Then, in order to estimate the potential carcinogenic risk of the mixture of PAHs measured in Mexico City, the concentration of the individual PAH were multiplied by their corresponding toxic equivalent factor to determine the total BAPeq. The calculated values of annual BAPeq for PM$_(10) and PM$_(2.5) were 2.3 and 2 ngm$^(-3) respectively than exceed the proposed standard. Nevertheless, in the dry-cold season the BAPeq reached values up to 3.6, maybe due to the atmospheric stability and the use of more fuel during the winter. These results indicate that the inhabitants of Mexico City are exposed to a higher risk health due to the presence of atmospheric PAHs, specially during the cold months.