Inhalation exposure to ambient polycyclic aromatic hydrocarbons and lung cancer risk of Chinese population

Abstract

An Euler atmospheric transport model (Canadian Model for Environmental Transport of Organochlorine Pesticides, CanMETOP) was applied and validated to estimate polycyclic aromatic hydrocarbon (PAH) ambient air concentrations at ground level in China based on a high-resolution emission inventory. The results were used to evaluate lung cancer risk for the Chinese population caused by inhalation exposure to PAHs. The uncertainties of the transport model, exposure, and risk analysis were assessed by using Monte Carlo simulation, taking into consideration the variation in PAH emission, aerosol and OH radical concentrations, dry deposition, respiration rate, and genetic susceptibility. The average benzo[a]pyrene equivalent concentration (B[a]P(eq)) was 2.43 [ approximately 1.29-4.50 as interquartile range (IR)] ng/m(3). The population-weighted B[a]P(eq) was 7.64 (IR, approximately 4.05-14.1) ng/m(3) because of the spatial overlap of the emissions and population density. It was estimated that 5.8% (IR, approximately 2.0-11%) of China's land area, where 30% (IR, approximately 17-43%) of the population lives, exceeded the national ambient B[a]P(eq) standard of 10 ng/m(3). Taking into consideration the variation in exposure concentration, respiration rate, and susceptibility, the overall population attributable fraction (PAF) for lung cancer caused by inhalation exposure to PAHs was 1.6% (IR, approximately 0.91-2.6%), corresponding to an excess annual lung cancer incidence rate of 0.65 x 10(-5). Although the spatial variability was high, the lung cancer risk in eastern China was higher than in western China, and populations in major cities had a higher risk of lung cancer than rural areas. An extremely high PAF of >44% was estimated in isolated locations near small-scale coke oven operations.

Fig. 1.

Spatial distribution of annual mean air concentrations of B[a]P at 1.5 m above the ground in China (South China Sea not included) in 2003. The results are presented in log scale.

Fig. 2.

Geographic distribution of population-weighted annual mean B[a]P_eq in ambient air 1.5 m above the ground in China (South China Sea not included) in 2003 (Left, log scale) and the cumulative frequency distributions of annual mean B[a]P_eq without (blue curves) and with (red curves) population weighting (Right). The dashed curves show the 25th and the 75th percentiles derived from the Monte Carlo simulation. The two red lines show the Chinese national standard (10 ng/m³) and WHO guideline (1 ng/m³) for B[a]P_eq in ambient air.

Fig. 3.

The cumulated frequency distributions of PAF for lung cancer induced by inhalation exposure to PAHs in China (South China Sea not included). The results were derived with (brown curves) and without (blue curves) taking into consideration the variation in respiration rate and susceptibility. The 25th and 75th percentiles are presented as dashed curves.