Indoor Exposure to Selected Air Pollutants in the Home Environment: A Systematic Review

Abstract

Background: There is increasing awareness that the quality of the indoor environment affects our health and well-being. Indoor air quality (IAQ) in particular has an impact on multiple health outcomes, including respiratory and cardiovascular illness, allergic symptoms, cancers, and premature mortality. (2) Methods: We carried out a global systematic literature review on indoor exposure to selected air pollutants associated with adverse health effects, and related household characteristics, seasonal influences and occupancy patterns. We screened records from six bibliographic databases: ABI/INFORM, Environment Abstracts, Pollution Abstracts, PubMed, ProQuest Biological and Health Professional, and Scopus. (3) Results: Information on indoor exposure levels and determinants, emission sources, and associated health effects was extracted from 141 studies from 29 countries. The most-studied pollutants were particulate matter (PM2.5 and PM10); nitrogen dioxide (NO2); volatile organic compounds (VOCs) including benzene, toluene, xylenes and formaldehyde; and polycyclic aromatic hydrocarbons (PAHs) including naphthalene. Identified indoor PM2.5 sources include smoking, cooking, heating, use of incense, candles, and insecticides, while cleaning, housework, presence of pets and movement of people were the main sources of coarse particles. Outdoor air is a major PM2.5 source in rooms with natural ventilation in roadside households. Major sources of NO2 indoors are unvented gas heaters and cookers. Predictors of indoor NO2 are ventilation, season, and outdoor NO2 levels. VOCs are emitted from a wide range of indoor and outdoor sources, including smoking, solvent use, renovations, and household products. Formaldehyde levels are higher in newer houses and in the presence of new furniture, while PAH levels are higher in smoking households. High indoor particulate matter, NO2 and VOC levels were typically associated with respiratory symptoms, particularly asthma symptoms in children. (4) Conclusions: Household characteristics and occupant activities play a large role in indoor exposure, particularly cigarette smoking for PM2.5, gas appliances for NO2, and household products for VOCs and PAHs. Home location near high-traffic-density roads, redecoration, and small house size contribute to high indoor air pollution. In most studies, air exchange rates are negatively associated with indoor air pollution. These findings can inform interventions aiming to improve IAQ in residential properties in a variety of settings.

Liquid crystal display screens as a source for indoor volatile organic compounds

“…However, the "passive sampling" hypothesis seems unlikely given the two reasons discussed next. First, if the indirect source is the dominant source, given the ubiquitous presence of benzene and toluene (with high concentrations) in both indoor and outdoor environments (23,24,33,34), we would expect to observe high emissions of these two VOCs from LCD screens, which is in contrast with the flow cell results (Fig. 3).…”

Genome-wide DNA methylation analysis of pulmonary function in middle and old-aged Chinese monozygotic twins

“…Moreover, the mounting evidences have supported disease-associated methylation loci could be identified from peripheral samples [ 66 ]. Third, the non-shared environment for the individual siblings of MZ twins, such as occupational environment [ 67 ], residential environment [ 68 ], and mode of transport [ 69 ], could expose themselves to different levels of environmental pollutants, including particulate matter, nitrogen dioxide; volatile organic compounds, polycyclic aromatic hydrocarbons, and so on, which might directly affect pulmonary function [ 70 – 73 ], and cause different levels of DNA methylation [ 74 – 78 ] thereby indirectly influencing pulmonary function. However, due to the complicated causes of DNA methylation and the difficulty of monitoring for the external environmental exposure, we have not further analyzed the causes of DNA methylation.…”

Improving on estimates of the potential relative harm to health from using modern ENDS (vaping) compared to tobacco smoking

“…Nevertheless, such exposures are likely to be relatively minor given evidence that NNAL levels in non-smokers are typically 1-5% those of smokers (due to exposure to second-hand smoke) [23]. Also, although one study included results for a PAH [37], which has other sources (e.g., cooking emissions, vehicle emissions, and industrial air pollution [68]), this study had the advantages of being a randomised trial, thus such exposures should have been non-differential. But this study was still suboptimal for our purposes in terms of not also measuring PAH in a control group (non-ENDS using and non-smoking), but it did show that PAH levels declined significantly in those switching to exclusive vaping.…”