Table 1. Summary and comparison of studies involving air pollutants and related health outcomes.

Title of Article	Sample Size	Country	Age	Type of Pollutant	Outcome
Ambient air pollution and cardiovascular emergency department visits 42	4,407,535	United States	NA	CO NO2 PM2.5 Organic carbon Elemental carbon Oxygenated hydrocarbons	Visits for congestive heart failure linked with organic carbon (RR: 1.048, 95%CI: 1.007-1.091), elemental carbon (RR: 1.035, 95%CI: 1.003-1.068) and PM2.5 (RR: 1.055, 95%CI: 1.006-1.105) Visits for cardiovascular disease linked with organic carbon (RR: 1.026, 95%CI: 1.006-1.046), elemental carbon (RR: 1.020, 95%CI: 1.005-1.036), PM2.5 (RR: 1.033, 95%CI: 1.010-1.056), CO (RR: 1.017, CI: 1.008-1.027), NO2 (RR: 1.025, 95%CI: 1.012-1.039), and oxygenated hydrocarbons (RR: 1.029, 95%CI: 1.000-1.059) Visits for peripheral vascular and cerebrovascular disease linked with CO (RR: 1.031, 95%CI: 1.010-1.052), PM2.5 (RR: 1.050, 95%CI: 1.008-1.093) and NO2 (RR: 1.041, 95%CI: 1.013-1.069) Visits for ischemic heart disease linked with oxygenated hydrocarbons (RR: 1.066, 95%CI: 1.012-1.122) and NO2 (RR: 1.029, 95%CI: 1.005-1.053)
Traffic-related air pollution and asthma hospital readmission in children: a longitudinal cohort study 45	758	United States	1-16 years	Elemental carbon attributed to traffic	White children exposed to higher TRAP levels associated with higher rate of hospital readmission for asthma as compared to White children with low TRAP exposure levels (p = 0.03)
Traffic-related air pollution and obesity formation in children: A longitudinal, multilevel analysis 46	4257	United States	5-7 years	NOx	Non-freeway NOx levels correlated with BMI at 10 years of age (p < 0.05) and also growth rate (p < 0.05) over the entire 4 years of follow up
Association of childhood obesity with maternal exposure to ambient air polycyclic aromatic hydrocarbons during pregnancy 47	422 followed up to age 5 341 followed up to age 7	United States	Birth to 7 years	PM2.5 Polycyclic aromatic hydrocarbons	Highest levels of prenatal polycyclic aromatic hydrocarbon exposure correlated with higher BMI z score at both age 5 years (β = 0.39, 95%CI: 0.08-0.70) and age 7 years (β = 0.30, 95%CI: 0.01-0.59) Higher prenatal polycyclic aromatic hydrocarbon exposure correlated with elevated body fat percentage (β = 1.93, 95%CI: 0.33-3.54) and fat mass (β = 1.11, 95%CI: 0.10-2.11) but not with differences in lean mass at 7 years of age
Effects of air pollution exposure on glucose metabolism in Los Angeles minority children 48	429	United States	8-18 years	NOx	Non-freeway NOx correlated with elevated insulin and fasting glucose (p < 0.001), decreased insulin sensitivity (p = 0.02), and increased insulin secretion (p = 0.002) Total NOx correlated with elevated insulin and fasting glucose (p = 0.03) and increased insulin secretion (p = 0.047)
Longitudinal associations between ambient air pollution with insulin sensitivity, beta-cell function, and adiposity in Los Angeles Latino children 49	314	United States	8-15 years	NO2 PM2.5	Elevated long-term exposure to ambient air pollution (NO2 and PM2.5) associated with a faster decrease in insulin sensitivity (p = 0.02) during the study period and reduced insulin sensitivity at 18 years of age (p = 0.04 for NO2, p = 0.01 for PM2.5) Increased long-term mean ambient air pollution exposure during the study period correlated with higher fasting and 2-hour insulin levels (p < 0.05) Elevated NO2 and PM2.5 exposures correlated with greater increases in BMI and central adiposity in pre-existing overweight and obese children at start of study (p < 0.05)
Long-term exposure to traffic-related air pollution and insulin resistance in children: results from the GINIplus and LISAplus birth cohorts 50	5,991 from the GINIplus Study 3,097 from the LISAplus Study	Germany	Birth to 10 years	NO2 PM10 PM2.5	Increase in insulin resistance measured at 10 years of age correlated with increase in PM10 (p = 0.019) and NO2 (p = 0.005)
Long-term exposure to fine particulate matter and incidence of type 2 diabetes mellitus in a cohort study: effects of total and traffic-specific air pollution 51	4,814	Germany	45-75 years	PM10 PM2.5	Exposure to total PM10 potentially linked with higher frequency of type 2 diabetes incidence (RR: 1.20, CI: 1.01,1.31) Increase in 1 μg/m3 of PM originating from traffic sources (RR: 1.36, CI: 0.98,1.89 for PM10, RR: 1.36, CI: 0.97,1.89 for PM2.5) had higher toxicity than the same amount of total PM (RR: 1.05, CI: 1.00,1.10 for PM10, RR: 1.03, CI: 0.95,1.12 for PM2.5)

Abbreviations:

PM, particulate matter; NO_x, nitrogen oxide; NO₂, nitrogen dioxide; CO, carbon monoxide; TRAP, traffic-relation air pollution; BMI, body mass index; RR, relative risk or risk ratio