ERS/ATS workshop report on respiratory health effects of household air pollution

Abstract

Exposure to household air pollution (HAP) from solid fuel combustion affects almost half of the world population. Adverse respiratory outcomes such as respiratory infections, impaired lung growth and chronic obstructive pulmonary disease have been linked to HAP exposure. Solid fuel smoke is a heterogeneous mixture of various gases and particulates. Cell culture and animal studies with controlled exposure conditions and genetic homogeneity provide important insights into HAP mechanisms. Impaired bacterial phagocytosis in exposed human alveolar macrophages possibly mediates several HAP-related health effects. Lung pathological findings in HAP-exposed individuals demonstrate greater small airways fibrosis and less emphysema compared with cigarette smokers. Field studies using questionnaires, air pollution monitoring and/or biomarkers are needed to better establish human risks. Some, but not all, studies suggest that improving cookstove efficiency or venting emissions may be associated with reduced respiratory symptoms, lung function decline in women and severe pneumonia in children. Current studies focus on fuel switching, stove technology replacements or upgrades and air filter devices. Several governments have initiated major programmes to accelerate the upgrade from solid fuels to clean fuels, particularly liquid petroleum gas, which provides research opportunities for the respiratory health community.

FIGURE 1

Schematic of mechanisms underlying the enhancement of cigarette smoke-induced neutrophilic inflammation by wood smoke. In addition to activating the inflammatory pathway, prolonged exposure to cigarette smoke activates an anti-inflammatory pathway. Wood smoke at levels that do not induce inflammation blocks the cigarette smoke-induced anti-inflammatory pathway and thereby enhances cigarette smoke-induced airway inflammation in a synergistic fashion. See Awji et al. [49] for details.

FIGURE 2

Lung biopsy from a woman known to have cooked with biomass fuel. a) High-power view shows marked fibrosis of the bronchioles with accompanying black pigment. Very focal early interstitial fibrosis spreading away from the bronchioles is also present. b) Polarisation microscopy demonstrates numerous birefringent particles in the fibrotic airway wall.

FIGURE 3

A Patsari wood-burning stove. The stove has a closed combustion chamber surrounded by bricks. A flat pottery dish or metal hotplate (called a comal and used for cooking tortillas) is integrally built into the surface of the stove, which has a smaller entrance for feeding fuel and a flue that passes through the roof and conveys the smoke outdoors. Reproduced from [92] with permission.

FIGURE 4

a) Traditional open fire used for cooking, and b) the locally developed and constructed chimney woodstove, the plancha, in Guatemala. The chimney woodstove has a thick metal heating surface for cooking tortillas and holes with removable concentric rings for pots, a firebrick combustion chamber with baffling, a concrete and brick body, tile surfaces around the cooking area, dirt and pumice stone insulation, a metal fuel door, and a metal chimney with a damper. Infants and toddlers are highly exposed to combustion smoke as they are carried on their mother’s back while she cooks, a common cultural practice in Guatemala and other regions. Reproduced from [91] with permission.