Association of traffic-related hazardous air pollutants and cervical dysplasia in an urban multiethnic population: a cross-sectional study

Abstract

Background: Human papillomavirus (HPV) infection is a necessary cause in the development of cervical cancer; however, not all women infected with HPV develop cervical cancer indicating that other risk factors are involved. Our objective was to determine the association between exposure to ambient levels of common traffic-related air toxics and cervical dysplasia, a precursor lesion for cervical cancer.

Methods: The study sample consisted of women enrolled in a Phase II clinical trial to evaluate diagnostic techniques for cervical disease in Houston, Texas. The current assessment is a secondary data analysis in which cases were defined as women diagnosed with cervical dysplasia, while those without cervical dysplasia served as controls. Residential census tract-level estimates of ambient benzene, diesel particulate matter (DPM), and polycyclic aromatic hydrocarbons (PAHs) were used to assess exposure. Census tract-level pollutant estimates were obtained from the United States Environmental Protection Agency. Multivariable logistic regression was used to estimate prevalence odds ratios (aOR) and 95% confidence intervals (CI) adjusted for age, race/ethnicity, education, smoking status, and HPV status.

Results: Women in the highest residential exposure categories for benzene and DPM had an increased prevalence of cervical dysplasia compared to the lowest exposure category (Benzene: aOR [95% CI] for high exposure = 1.97[1.07-3.62], very high exposure = 2.30[1.19-4.46]. DPM: aOR [95% CI] for high exposure = 2.83[1.55-5.16], very high exposure = 2.10[1.07-4.11]). Similarly, women with high residential exposure to PAHs had an increased prevalence of cervical dysplasia (aOR [95% CI] = 2.46[1.35-4.48]). The highest PAH exposure category was also positively associated with cervical dysplasia prevalence but was not statistically significant. Assessment of the combined effect of HAP exposure indicates that exposure to high levels of more than one HAP is positively associated with cervical dysplasia prevalence (p for trend = 0.004).

Conclusions: Traffic-related HAPs, such as benzene, DPM, and PAHs, are not as well-regulated and monitored as criteria air pollutants (e.g., ozone), underscoring the need for studies evaluating the role of these toxicants on disease risk. Our results suggest that exposure to traffic-related air toxics may increase cervical dysplasia prevalence.

Figure 1

Correlations between traffic-related hazardous air pollutant levels. Scatterplots of (A) diesel particulate matter (DPM) and benzene, (B) polycyclic aromatic hydrocarbons (PAHs) and benzene from the 1999 United States’ Environmental Protection Agency’s (U.S. EPA) Assessment System for Population Exposure Nationwide’s (ASPEN) model for Texas census tracts included in the current assessment.