Table 4.

Studies of effect modification of social stresses on chemical health impacts.

Health outcome	Chemical stressor	Non-chemical stressor	Results	Reference
Mortality
Short-term studies	CoH (PM indicator); SO2	SES indicators: unemployment, poverty, education, high manufacturing employment	Effect modification by SES measures; slightly higher relative risks and more significant results across the lag periods tested	[89]
	PM2.5	SES indicators: household income, poverty, education	Effect modification only significant for household income	[90]
	PM10 adjusted for O3, SO2, NO2, CO	SES indicators: education, annual income	No effect modification by SES	[91]
	PM10	SES indicator: education	Evidence of weak effect modification by education	[87]
	PM10	SES indicators: unemployment, poverty level, education	No effect modification by SES	[92]
	PM10, O3	SES indicator: sociospatial development index (based on homes with electricity, homes with piped water and drainage, literacy, and indigenous language speakers)	PM10 not associated with mortality; ozone was significantly associated with mortality, but no consistent effect modification observed	[93]
	PM10	SES indicators: education, income, living in slums	Effect of PM on respiratory mortality was negatively correlated with % college education, % family income > $3,500, living in slums	[94]
	PM10	SES indicator: composite index	Larger effect in higher SES areas but not statistically significant	[95]
	TSP, CO, NO2, SO2, O3, PM10, CoH, PM10–2.5	SES indicator: income	Only NO2 was associated with mortality in low income groups	[96]
Short-term studies	PM10	SES indicator: education	Larger mortality risk estimates were observed in least-educated for all cause, respiratory, and heart disease-related mortality	[97]
	PM10	SES indicator: income, index that includes education, occupation, unemployment rate, family size, crowding, home ownership	The PM10-mortality association was greater in lower income and lower SES communities	[98]
	O3	SES indicator: education, income, unemployment, poverty	Effect modification only for unemployment; higher mortality rates for higher unemployment	[99]
Long-term studies	PM2.5, sulfates	SES indicator: education	Significant effects for both PM2.5 and sulfates in least educated	[84]
	PM2.5, sulfates	SES indicator: education	Patterns are similar to previous study but effect modification is less clear; for ischemic heart disease pattern was reverse (most educated has greatest risk)	[85]
	TSP, BS, NO2	SES indicator: education	No effect modification by educational attainment	[100]
	BS	SES indicator: education	No effect modification by educational attainment	[101]
	TSP, SO2	SES indicator: income	Relative risks were higher for the low household income category	[102]
	Air pollution index: sum of standardized measures of TSP and SO2	Deprivation index (includes unemployment and education)	No effect modification	[103]
Neurological effects	Blood lead	SES indicator: income	Cognitive deficits (Kaufman Assessment Battery) associated with neonatal blood lead only in poorer families	[104]
	Blood lead	SES indicator: income	No modifying effect of SES on blood lead-learning/IQ association, but observed trend of greater vulnerability in lower SES subgroup	[105]
	Blood lead	SES indicator: parents’ occupational prestige	Modifying effects by SES were observed for IQ and blood lead, but interaction became non significant when adjusted for other factors (age at testing, iron status, birth weight, etc.)	[106]
	Blood lead	SES indicator: composite index including education and father’s occupation	Effect modification of lead-related decreased performance in visual-motor integration and choice reaction tests	[107]
	Blood lead	SES indicators: Hollingshead’s Four-Factor Index of Social Class, a measure of parents’ occupational and educational achievements	Modifying effects by SES were observed for Mental Development Index and blood lead only at ages 18 to 24 months	[108]
	Bone lead	SES indicators: neighborhood psychosocial hazards (neighborhood violent crimes, 911 calls, etc.)	Psychosocial stress exacerbated effects of lead on 3 of 7 cognitive measures	[109]
Cardiovascular Disease	Lead (bone lead)	SES indicators: stress (based on standardized questionnaire and self-reported)	Effects of lead on hypertension were more pronounced in stressed individuals	[110]
	O3, CO, NO2	SES indicators: education, income	No effect modification by SES on cardiac hospital admissions	[111]
Asthma and other respiratory diseases	NO2 (proxy for traffic)	SES indicators: exposure to violence	Elevated risk of developing asthma with increased NO2 exposure only in children with higher exposure to violence	[69]
	Traffic-related air pollution (Nitrogen Oxides)	SES indicators: parental education, parental stress	High parental stress was associated with higher incidence of traffic-related risk of developing asthma. An increased risk of asthma was also observed for low SES families exposed to air pollution	[112]
	O3, SO2, NO2	SES indicators: education, income	Greater hospitalizations for respiratory effects in lower education and lower income strata	[113]
	NO2, SO2, O3, CO	SES indicator: average household income adjusted for household size	Male children had higher asthma hospitalizations in low SES group with exposure to NO2; female children had higher asthma hospitalizations for SO2 in the low-income group. No associations for O3 or CO	[114]
	NO2	SES indicator: insurance status	Children without insurance had higher risk of asthma admissions than those with private insurance	[115]
	PM10, O3, sulfates, strong acidity	SES indicator: insurance status	The overall hospital admissions association for both O3 and PM10 was driven by the uninsured minority population	[116]
	NO2	Life stress	Greater inflammatory markers associated with high stress in low pollution exposure group	[117]

CoH = coefficient of haze; SO₂ = sulfur dioxide; PM₁₀ = particulate matter > 10 μm; O₃ = ozone; NO₂ = nitrogen dioxide; CO = carbon monoxide; TSP = total suspended particulate matter