Table 2.

Summary statistics and correlations of pollutant exposures over the first trimester (0–13 weeks of gestation) in 23 Tokyo wards, from 2013 to 2015.

	No. of women	Mean (SD)	Percentile				Pearson’s correlation coefficient
			25	50	75	IQR	Total PM2.5	Total carbon	OC	EC	Nitrate	Sulphate	Ammonium	Chloride	Sodium	Potassium	Calcium	Ozone	Temperature
Total PM2.5 (μg/m3)	83,454	16.8 (2.6)	14.9	16.1	18.5	3.62	1
PM2.5 components (μg/m3)a
Total carbon	67,706	4.0 (0.5)	3.7	4.1	4.3	0.62	−0.17*	1
OC	67,706	2.7 (0.4)	2.4	2.7	2.9	0.51	−0.22*	0.98*	1
EC	67,706	1.3 (0.2)	1.2	1.3	1.4	0.22	−0.01	0.87*	0.76*	1
Nitrate	67,706	1.4 (0.8)	0.6	1.3	2.1	1.48	−0.32*	0.57*	0.58*	0.43*	1
Sulphate	67,706	2.8 (1.0)	1.9	2.8	3.6	1.77	0.88*	−0.42*	−0.44*	−0.31*	−0.41*	1
Ammonium	67,706	1.5 (0.3)	1.2	1.5	1.7	0.56	0.70*	0.00	-0.02*	0.04*	0.32*	0.70*	1
Chloride	67,706	0.20 (0.14)	0.08	0.15	0.34	0.26	−0.60*	0.69*	0.70*	0.53*	0.84*	−0.72*	−0.07*	1
Sodium	67,706	0.15 (0.03)	0.12	0.15	0.17	0.06	0.52*	−0.32*	−0.31*	−0.29*	−0.72*	0.59*	0.04*	−0.80*	1
Potassium	67,706	0.07 (0.01)	0.06	0.07	0.08	0.02	0.06*	0.65*	0.61*	0.64*	0.24*	−0.15*	0.04*	0.22*	0.18*	1
Calcium	67,706	0.07 (0.02)	0.06	0.07	0.09	0.03	0.37*	−0.12*	−0.17*	0.04*	0.17*	0.43*	0.58*	−0.14*	0.18*	0.40*	1
Ozone (ppb)b	83,454	35.9 (7.4)	29.3	35.0	42.7	13.41	0.83*	−0.46*	−0.45*	−0.41*	−0.41*	0.86*	0.59*	−0.75*	0.65*	−0.02*	0.50*	1
Ambient temperature (°C)	83,454	16.5 (7.0)	9.7	16.7	23.3	13.54	0.55*	−0.36*	−0.39*	−0.23*	−0.87*	0.57*	−0.08*	−0.85*	0.86*	−0.08*	−0.12*	0.52*	1

EC elemental carbon, IQR interquartile range, OC organic carbon, SD standard deviation.

*p value <0.05.

^aExposure to PM_2.5 chemical components was assigned to 67,706 women, because these measurements only began in April 2013, which the study began in January of that year.

^bDaily maximum 8-h mean concentrations.