Table 1.

Air pollution exposure and atopic outcomes (only papers from 2019 until present)

Exposure	Author, Year	Country	Atopic outcome evaluated	Findings
Air pollution	Noh, 201961	S. Korea	AD	Children with AD have variable responses to increased air pollution; overall, PM10, NO2, SO2, and CO correlated with increased AD symptoms.
	Gallant, 202036	Canada	Sensitization	Children who were exposed to ETS at 2 years of age were significantly more likely to have a positive skin prick test to any of 14 common allergens at 2 years old.
	Granum, 202056	UK, France, Spain, Greece, Lithuania, Norway (multicenter)	AR, itchy rash, eczema, FA	Increased PMabs exposure correlated with decreased risk of AR. Early childhood exposure to pollutants did not correlate with AR risk. The authors did not find correlations between prenatal exposures and the allergic outcomes of AD or FA, nor did they find correlations between childhood exposures with any allergic outcome studied.
	Kuiper, 202064	Norway, Sweden	AR	Paternal exposure to O3 (medium level) correlated with increased risk of offspring AR. Maternal exposure to PM10 (high level) also correlated with offspring’s increased risk of AR.
	Min, 202059	S. Korea	AR, AD	Both NO2 and PM10 were associated with AD risk and symptoms. PM2.5 tended to correlate with AD symptoms and diagnosis as well, but this finding was not statistically significant.
	To, 202057	Canada	AR, AD	The combined exposure of O3 and NO2 at birth correlated with risk for AD in a dose-dependent manner. In contrast, early PM2.5 exposure did not correlate with risk for allergic outcomes.
	Wang, 202065	China	AR	Increased levels of pollutants (PM2.5, PM10, SO2, NO2, and CO) were associated with significantly more outpatient AR visits that same day; all associations were stronger for patients under the age of 15.
	Guo, 202167	China	AR, AD	Increased levels of NO2, PM2.5, and PM10 during the second trimester of pregnancy increased a child’s risk of developing allergic disease.
	Hao, 202166	China	AR	TRAP exposure in preschool children correlated with AR prevalence; more specifically, increases in PM10 and NO2 exposure increased one’s risk of developing AR.
	Melén, 202153	Sweden, Germany, The Netherlands	Sensitization	There was not a consistent association of air pollution with sensitization to any common allergen up to age 16. Allergen-specific analyses suggested an increase in NO2 correlated with increased risks of birch sensitization. Additionally, PM2.5 exposure at birth may relate to sensitization to the grass allergen Phl p 1 and the cat allergen Fel d 1.
	Wang, 202137	Taiwan	AD	Increased exposure to THCs, NMHCs, and CH4 (hydrocarbon air pollutants) correlated with higher rates of developing AD in childhood.
	Yao, 202143	Taiwan	AD	Prenatal PM2.5 exposure from week 7–17 of gestation correlated with increased risk of developing AD in childhood, particularly during the 12th week.
	Hu, 202263	China	AD	NO2 levels correlated with more outpatient visits for AD.
	Liu, 202268	China	AR	Exposure to outdoor air pollution, in the year prior to conception, throughout pregnancy, and within the past 12 months of survey administration, correlated with aggravated AR symptoms in the fall. Specifically, symptoms were associated with pre-conception and prenatal SO2 and NO2 exposure, and recent PM10 and NO2 exposure.
	Park, 202239	S. Korea	AD	Increased PM2.5, PM10, SO2, and CO all correlate with increased monthly AD visits; this was not seen for O3 nor NO2.
	Wu, 202269	China	AR	Exposure to pollutants (PM2.5, PM10, NO2, SO2) were not correlated with increased risk of outpatient visit for AR in children under the age of 18.
	Ye, 202262	China	AD	Increased levels of air pollutants (SO2, NO2, but not O3) were associated with increased AD outpatients. Patients less than 7 years old were most sensitive to air pollutants (including PM10, SO2, and NO2). Factors such as season or other pollutants were seen to significantly heighten the harmful effects of SO2 and NO2.

AD, atopic dermatitis; AR, allergic rhinitis; FA, food allergy