"We spend almost all of our time indoors and this can impact public health in a negative way," the University of California's William Nazaroff told environmentalresearchweb. "If we don't pay attention to this issue, the forces of climate change will make things worse."

Nazaroff reviewed the literature in order to bring together a number of elements that have been studied separately. The paper, published in Environmental Research Letters (ERL) , identifies three classes of factors that have important influence on indoor air quality: pollutant attributes, building characteristics and human behaviour. Both pollutant sources and removal processes govern pollutant concentrations indoors, and these concentrations in combination with human occupancy determine exposure.

According to the review, climate change may cause an increase in the concentrations of certain outdoor pollutants, increasing indoor exposure. It could also affect indoor air quality indirectly through human responses to climate change, such as lower ventilation rates to reduce energy use, or the increased use of air conditioning due to warmer conditions.

Reactions to climate emergencies also pose a threat to public health – the use of portable electric generators during severe or frequent storms is a key example given in the paper. Poisoning episodes have been associated with storm events due to carbon monoxide emitted from the exhausts of gasoline-burning generators, causing life-threatening illness.

"Though professionals are aware of the concern, public understanding is incomplete," said Nazaroff. "A few people making poor or unconfirmed decisions can lead to serious adverse health consequences."

Combustion (for cooking, heating and smoking, for example) is identified as a major source of both outdoor and indoor air pollution. Radon and volatile and semivolatile organic compounds are important indoor pollutants. Outdoors the main pollutants of concern are particulate matter and ozone. Increases in wildfires, pollen and windblown dust could all increase levels of particulate matter outdoors that could enter indoor environments.

Chemicals with endocrine-disrupting properties are also identified as a potential threat to air quality in a climate-change regime. Nazaroff explained that allowing indoor environments to become warmer to reduce carbon emissions could alter the behaviour of endocrine-disrupting chemicals.

"This finding fits into a broader theme that indoor issues matter for public health," he said. "Attention is skewed and outdoor issues get much more attention than indoor issues. The research community needs to be reminded that the air around us indoors matters as much as, or even more than, outdoor air."

Nazaroff's paper is part of the ERL Focus on Environmental Assessments in the Built Environment.

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