Indoor Air Pollution: Health Impacts
About half of the world’s population, and 75 percent of households in India, use biofuels and biomass, including wood, charcoal, crop residues and dung, to prepare food and heat their homes. More than 70 percent of India’s population lives in rural areas. Cooking accounts for about 60 percent of the overall energy and 80 percent of the non-commercial energy used in rural India. More than 90 percent of the cooking is done with fire wood and bovine dung, i.e, cow-dung.
Cooking fires, often open fires in enclosed spaces, lead to both indoor and outdoor air pollution, with detrimental consequences for local health. Several international studies have documented that indoor air pollution leads to 400,000-550,000 premature deaths in India from acute lower respiratory infections and chronic obstructive pulmonary disease. Air pollution-related premature deaths can be as high as 2.5 million according to another study (Pachauri and Sridharan, 1998).
The burden falls disproportionately on women and children, who inhale soot and other particles from smoke released by the burning of biofuels. The health impact of India’s cooking fires is not unusual in the developing world: solid fuel use accounts for 4.8 percent of Sub-Saharan Africa’s disease burden, 2.5 percent of the disease burden in China, and just under 1 percent of the disease burden in the poorer Latin American countries.
Documenting Health Impacts
Incomplete combustion of biomass fuels in inefficient stoves within poorly ventilated spaces results in emissions of respirable particles, gases (such as CO and NO) and many volatile and non-volatile organic compounds, including carcinogens such as benzo[a]pyrene, formaldehyde, and benzene. Average indoor concentrations of PM can be as high as several mg/m, with peak concentrations an order of magnitude higher. Women and young children are at the highest risk of exposures. Assessments of the burden of disease attributable to use of solid fuel use in India have put the figure at 3–5 percent of the national burden of disease.
The strength of evidence for the estimated burden is the strongest for incidence of chronic bronchitis in women and acute lower respiratory infections (ALRI) in children. Contributions to other adverse health outcomes such as asthma, tuberculosis, cataracts and adverse peri-natal outcomes are likely to be significant as well. Recently, The International Agency for Research on Cancer (IARC) has concluded that indoor emissions from household combustion of biomass fuel (mainly wood) are “probably carcinogenic to humans (Group 2A)”.
Although a large body of epidemiological studies have contributed to understanding health risks related to biomass fuel use, few provide quantitative exposure data. Most studies in the region have used reported “solid fuel use” as a proxy indicator of exposure. More recently, large-scale studies carried out in Southern India across multiple exposure configurations, in addition to quantifying multiple pollutants, have provided considerable understanding of spatial, temporal and other determinants of population exposure related to solid fuel use in the region.
Assessing Intervention Effectiveness
From a policy standpoint, although it is health effects that drive concern, it is too late by the time they occur to use disease rates as an indicator of the need for action in particular places. In addition, because these diseases have other causes as well, it is difficult and costly to conduct careful epidemiological studies to quantify the disease burden due to indoor air pollution, and to distinguish it from the burden due to other common risk factors. Improved knowledge of exposures then becomes a useful tool for determining effective intervention options. Therefore, we propose to build the evidence for expected health improvements in the first phase through documentation of exposure reduction and subsequently through reduction in incidence and severity of diseases.
We (KB) have considerable previous experience in population based exposure assessment methods. Using a combination of area and personal sampling devices together with detailed time-activity records, exposure reductions can be convincingly demonstrated. We will also deploy direct read-out devices with a detailed observational diary entry in a sub-set of households to gain an insight into exposure attributions from individual household activities as well as understand socio-cultural determinants likely to be important in sustainability of interventions. Biomarkers of exposure and early biological effect monitored in a sub-set of individuals will provide evidence for reduction of body burden.
We (KB) have used cross-sectional and longitudinal health monitoring methods in rural households extensively to establish the baseline situation with respect to indoor air pollution related health end-points. Some of these include recording self –reported symptoms, performing on-site serial lung function tests and physician assessments for ALRI/ Asthma/ COPD. While some outcomes will require considerable follow up during several phases of the intervention, an acute outcome such as children’s ALRI is easily amenable to assessment within a period of a year or two. More complicated assessments such as lung function improvements, recording of adverse pregnancy/low birth-weight outcomes can be piloted during the initial phases with plans drawn up for follow up epidemiological surveillance. We will engage in extensive capacity building of local health professionals to recognize, evaluate and manage the health hazards related to indoor air pollution. Wherever feasible, the Comparative Risk Assessment (CRA) protocols of WHO will be used in to calculate burden of disease burdens (if for e.g. the proposed interventions reduce exposures to the counterfactual levels used in the CRA procedure).Economic Development