processes that do not burn much fuel can nevertheless raise substantial IAQ concerns and adversely affect public health.

Combustion might be the most important source of air pollution. Indoor combustion for cooking, lighting, and heating has a long and diverse history of contributing to air-pollution exposure. Lopez et al. (2006) ranked “indoor air pollution from [burning] solid fuels” as one of the top 10 leading causes of global mortality and disease. That ranking is based mainly on the use of biomass and coal in rural parts of developing countries. Unvented or incompletely vented combustion also occurs to a substantial extent in developed countries and has demonstrable effects on indoor pollutant concentrations and exposures. Evidence associating those exposures with public-health consequences ranges from suggestive to clear and compelling. Exposures resulting from indoor combustion could be altered in the future in several ways associated with climate change. Influencing factors could include changing prevalence, frequency, or strength of indoor emission rates and also changes in building ventilation conditions.1 The following paragraphs summarize some of the concerns and provide references to document the nature and importance of the current problems.

Accidental Carbon Monoxide Poisoning

Carbon monoxide (CO) is produced by the incomplete combustion of a carbonaceous fuel. Inhaled CO forms carboxyhemoglobin in the blood, whose presence interferes with transport and delivery of oxygen to tissues and organs. Excessive acute exposures result in illness or death. Chronic lower-level exposures may also have health consequences, but the available empirical evidence is weaker than that for acute poisonings.

CO is regulated as a pollutant in ambient air. Mainly through strong improvements in automotive emission-control technology, urban air CO levels have become well controlled, and almost every area of the United States meets the National Ambient Air Quality Standard for CO (EPA, 2010b).

Despite improvement in outdoor levels, CO remains an important air pollutant. Over the past few decades, hundreds of accidental and fatal acute CO poisonings have occurred each year in the United States (Cobb and Etzel, 1991; King and Bailey, 2008; Mott et al., 2002). The incidence has declined substantially. One important factor is improvements in the control of motor-vehicle emissions. Mott et al. analyzed CO-associated mortality statistics and concluded that, “if rates of unintentional CO-related deaths had remained at pre-1975 levels, an estimated additional 11,700 motor-vehicle-related CO poisoning deaths might have occurred by


1 Building tightening and reduced ventilation rates are further discussed in Chapter 8.

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