Indoor air pollution in rural north-east India: Elemental compositions, changes in haematological indices, oxidative stress and health risks.

Chronic smoke exposure, emitted by biomass fuel burning leads to many diseases, which are originated due to oxidative stress. The present study investigated the levels of PM2.5, PM10 and PM2.5 bound trace metals released during cooking with fuelwood and subsequent changes in haematological parameters along with oxidative stress in rural tribal women of northeast India exposed to wood smoke. The levels of PM2.5, PM10 and trace metals associated with PM2.5 (nickel, cobalt, manganese, zinc, cadmium, lead and copper) were measured. In addition, blood samples were analyzed for concentrations of different blood related parameters (haemoglobin, platelet count, red blood cells and white blood cells) and levels of antioxidants (reduced glutathione, superoxide dismutase, and catalase). Plasma malondialdehyde (MDA) was measured as a biomarker of lipid peroxidation. Health risk assessment was done to assess the potential risk posed by inhalation of fine particles emitted from cooking with fuel wood. Levels of both PM2.5 and PM10 were higher in wood users compared to LPG users during cooking period (644.4 ± 368.3 µg/m³ vs 50 ± 23.8 µg/m³; 915 ± 441.3 µg/m³ vs 83.3 ± 33 µg/m³) and it exceeded the permissible limits of WHO. Levels of trace metals during the cooking period in fuel wood users were significantly higher than LPG users (p = 0.01). After controlling possible confounders, both platelet count and white blood cells (WBC) had a significant positive association with PM2.5and PM10. Similarly, haemoglobin had a negative association with both PM2.5 and PM10. Depleted levels of antioxidant enzymes and increase in lipid peroxidation (MDA) suggest a close association with pollutants released from wood smoke, indicating oxidative stress in women who used fuelwood for cooking. The total hazard quotient (HQ) of 0.11 was within the acceptable limit (i.e., 1.0). The total excess lifetime cancer risk (ELCR) was 5.4 × 10-6 which is five times higher than the acceptable limit of 1.0 × 10-6. Individual carcinogenic risk of Ni (2.3 × 10-6) and Cd (3.1 × 10-6) were also higher compared to acceptable limit. These results indicate that tribal women cooking with wood are at greater risk of developing cancer and also give support to the positive association between wood smoke and oxidative stress.