Table 2.

Annual average ${\mathrm{PM}}_{2.5}$ component estimates at the child’s residence for 9- to 10-year-old participants from the ABCD Study cohort ($n=\mathrm{8,589}$), 2016–2018.

$\mathrm{P}{\mathrm{M}}_{2.5}$ components	Mean	SD	IQR
Carbons and ions (${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$)
OC	1.90	0.46	0.57
EC	0.53	0.16	0.19
${\mathrm{NO}}_3^{-}$	0.92	0.35	0.56
${\mathrm{SO}}_4^{2-}$	0.92	0.28	0.42
${\text{NH}}_4^{+}$	0.30	0.12	0.19
Trace elements (${\text{ng}/\mathrm{m}}^3$)
Br	2.58	0.59	0.57
Ca	47.93	21.08	31.82
Cu	4.65	1.67	2.28
Fe	65.83	24.51	30.79
K	63.08	9.77	13.34
Ni	0.84	0.26	0.26
Pb	4.54	1.24	1.36
Si	82.86	37.32	61.22
V	0.37	0.2	0.21
Zn	9.34	4.1	4.13

Note: Br, bromine; Ca, calcium; Cu, copper; EC, elemental carbon; Fe, iron; IQR, interquartile range; K, potassium; ${\text{NH}}_4^{+}$, ammonium; Ni, nickel; ${\mathrm{NO}}_3^{-}$, nitrate; OC, organic carbon; Pb, lead; ${\mathrm{PM}}_{2.5}$, fine particulate matter with aerodynamic diameter $\le 2.5\mathrm{\mu }\mathrm{m}$; SD, standard deviation; Si, silicon; ${\mathrm{SO}}_4^{2-}$, sulfate; V, vanadium; Zn, zinc.