Air pollution and its effects on health – Case studies, India

To investigate the health impact of vehicular pollution of Kolkata (former Calcutta), a cross-sectional study was carried out during 2007-2010 among 932 male non-smoking residents of the city and 812-ageand gender-matched rural subjects as control. The urban group included 460 men who were occupationally exposed to vehicular pollution: 56 traffic policemen, 188 street hawkers, 82 auto rickshaw drivers, 78 bus drivers and 56 motor mechanics. Remaining 472 participants from the city were office employees. Compared with control, urban subjects had increased prevalence of respiratory symptoms, asthma, headache and reduced lung function, chronic obstructive pulmonary disease and hypertension. The changes, more prevalent among occupationally exposed subjects, were positively associated with PM10 level in ambient air. The urban subjects also showed increased levels of pro-inflammatory cytokines and chemokines in plasma, cytological changes suggesting inflammation in the airways, altered immunity (depleted number of CD4+ T cells and CD19+ B cells but increased number of CD16+CD56+ NK cells), leukocyte activation in terms of expression of CD11b/CD18 and production of myeloperoxidase and elastase, along with upregulation of platelet P-selectin expression and raised soluble P-selectin in plasma,implying platelet hyperactivity. Urban participants illustrated excess generation of reactive oxygen species concomitant with depletion of superoxide dismutase and total antioxidant status, suggesting oxidative stress. Moreover, they showed increased chromosomal breakage and DNA damage and elevated level of expression of γ-H2AX protein suggests that the damage was at the level of DNA double strands. Despite this, the expressions of DNA damage repair proteins Mre-11 and Ku70 were only modestly up-regulated, implying insufficient DNA repair. Besides, pro-survival signaling by protein kinase B was activated and metaplasia and dysplasia of airway cells were increased suggesting triggering of the carcinogenesis process in the lung. In essence, chronic exposure to vehicular pollution of Kolkata reduces lung function, increases blood pressure, suppresses immunity, and enhances cancer risk in the lung.