An Exposure-Mortality Relationship for Residential Indoor PM2.5 Exposure from Outdoor Sources

Abstract

A large proportion of particulate air pollution exposure in urban areas occurs due to the penetration of outdoor pollution into the residential indoor environment. Theoretical considerations suggest that quantifying health effects due to changes to indoor particulate concentrations derived from outdoor sources requires the adjustment of exposure-response coefficients based on epidemiological studies of outdoor air. Using the PM 2.5 -mortality coefficient from the American Cancer Society (ACS) cohort study as an example, we developed a theoretical model to quantify the relationship between the published coefficient and one based on personal exposure, and explored how this adjusted coefficient might be applied to changes in indoor PM 2.5 from outdoor sources. Using a probabilistic approach, our estimated average mortality coefficient for personal PM 2.5 exposure is 30-50% greater than the ACS coefficient. However, since the indoor PM 2.5 of outdoor origin accounts for only a proportion of the overall exposure, the average net adjustment required for indoor exposure is very modest. The results suggest that it is generally appropriate to apply unadjusted exposure-response functions derived from cohort studies to assess the health impact of changes in indoor particle concentrations from outdoor sources. However, it may be important to re-scale the coefficients for assessing exposures of population groups who spend a greater proportion of their time at home.

Outcome‐based ventilation: A framework for assessing performance, health, and energy impacts to inform office building ventilation decisions

“…Uncertainty remains regarding the role of indoor exposure in longitudinal cohort studies based on concentrations at outdoor monitoring stations . While many studies have applied outdoor C‐R functions directly to indoor air concentrations, a number have also modified outdoor C‐R functions for indoor application . We followed the latter studies and extended them by considering total exposure holistically and adjusting the response coefficient to correspond to personal exposure concentration, rather than monitoring station concentration.…”

“…49 While many studies have applied outdoor C-R functions directly to indoor air concentrations, 20,23,36 a number have also modified outdoor C-R functions for indoor application. 39,50 We followed the latter studies and extended them by considering total exposure holistically and adjusting the response coefficient to correspond to personal exposure concentration, rather than monitoring station concentration. Conceptually, we simply inserted a personal exposure correction factor…”

Towards the Integrated Study of Urban Climate, Air Pollution, and Public Health

“…They also highlight the importance of assessing local scale impacts, suggesting that whilst the increased use of domestic wood burners would likely result in negative impacts on health, there are significant economic and health gains to be made by promoting strategies that reduce traffic-related emissions by promoting active transport modes such as cycling and walking. Milner et al [20] further demonstrate the need for careful consideration of the links between climate, air pollution, and health. They argue that whilst reductions in GHG emissions through improvements in residential energy efficiency achieved by increased insulation may have appreciable near-term net benefits to health due to better indoor thermal regulation and reduced exposure to outdoor pollutants, these may be offset by increased exposure to indoor sources of pollution due to reduced ventilation.…”

“…They note the socio-economic differences in health outcomes, with the greatest benefits realised by males and those living in areas with below-average median household income. The importance of understanding the impact of air pollution on health in the context of total personal exposure and, particularly, the quality of the indoor environment is also highlighted in a methodological analysis by Milner et al [20].…”

“…Effective urban growth and regeneration planning, which pays attention to the creation of more sustainable transportation options and building climate control measures, is required to maintain and improve public health in cities. Efforts need to target reduced emissions through the promotion of active modes of transport and home heating/cooling measures [13,20]. The provision of less polluted [19] and less noisy outdoor spaces, which promote exercise and wellbeing, will ultimately reduce the burden of non-communicable diseases [11,12].…”