Bioaerosol and microbial exposures from residential evaporative coolers and their potential health outcomes: A review

Evaporative cooling is an energy efficient form of air conditioning in dry climates that functions by pulling hot, dry outdoor air across a wet evaporative pad. While evaporative coolers can help save energy, they also have the potential to influence human health. Studies have shown residential evaporative coolers may pull outdoor air pollutants into the home or contribute to elevated levels of indoor bioaerosols that may be harmful to health. There is also evidence that evaporative coolers can enable a diverse microbial environment that may confer early‐life immunological protection against the development of allergies and asthma or exacerbate these same hypersensitivities. This review summarizes the current knowledge of bioaerosol and microbiological studies associated with evaporative coolers, focusing on harmful and potentially helpful outcomes from their use. We evaluate the effects of evaporative coolers on indoor bacterial endotoxins, fungal β‐(1 → 3)‐D‐glucans, dust mite antigens, residential microbial communities, and Legionella pneumophila. To our knowledge, this is the first review to summarize and evaluate studies on the influence that evaporative coolers have on the bioaerosol and microbiological profile of homes. This brings to light a gap in the literature on evaporative coolers, which is the lack of data on health effects associated with their use.