Table 2

Adjusted* prevalence OR and 95% CI of learning disability by category of seven persistent organic pollutants

POPs	Detection rate (%)		Non-detectable POPs	Detectable POPs	p Value
POP, persistent organic pollutant.
*Adjustment for age, race/ethnicity, sex, poverty index ratio, mother’s age at pregnancy, cigarette smoking during pregnancy, birth weight, body mass index and saturated fat intake.
†Median (interquartile range).
3,3′,4,4′,5-penta chlorobiphenyl	22.4	Concentration (ng/g of lipid)†		9.1 (6.7–20.6)
		Cases/n	33/208	11/69
		Prevalence (%)	15.9	15.9
		Adjusted* OR (95% CI)	Referent	1.26 (0.47 to 3.32)	0.62

1,2,3,4,6,7,8-hepta chlorodibenzo-p-dioxin	30.5	Concentration (pg/g of lipid)†		38.9 (30.2–50.9)
		Cases/n	24/191	20/86
		Prevalence (%)	12.6	23.3
		Adjusted* OR (95% CI)	Referent	2.08 (1.17 to 3.68)	0.02

1,2,3,4,6,7,8,9-octa chlorodibenzo-p-dioxin	26.8	Concentration (pg/g of lipid)†		23.0 (18.5–30.2)
		Cases/n	24/199	20/78
		Prevalence (%)	12.1	25.6
		Adjusted* OR (95% CI)	Referent	2.72 (1.24 to 5.99)	0.02

1,2,3,4,6,7,8-hepta chlorodibenzofuran	31.9	Concentration (pg/g of lipid)†		10.0 (7.8–14.8)
		Cases/n	23/189	21/88
		Prevalence (%)	12.2	23.9
		Adjusted* OR (95% CI)	Referent	2.18 (1.15 to 4.15)	0.02

β-hexachlorocyclo-hexane	22.4	Concentration (ng/g of lipid)†		17.9 (14.6–26.4)
		Cases/n	38/201	6/76
		Prevalence (%)	18.9	7.9
		Adjusted* OR (95% CI)	Referent	0.37 (0.13 to 1.02)	0.05

Trans-nonachlor	25.4	Concentration (ng/g of lipid)†		10.9 (8.4–16.0)
		Cases/n	27/207	17/70
		Prevalence (%)	13.0	24.3
		Adjusted* OR (95% CI)	Referent	1.67 (0.46 to 6.14)	0.41

			Detectable<50th	Detectable⩾50th

p,p′-dichlorodiphenyl trichloroethane	100	Concentration (ng/g of lipid)†	75.3 (49.0–98.4)	278 (186–528)
		Cases/n	26/138	18/139
		Prevalence (%)	18.8	13.0
		Adjusted* OR (95% CI)	Referent	0.89 (0.24 to 3.37)	0.85