Table 2.

Mean annual air pollution exposure for ALS patients and controls.

Air pollutants ($\text{mean}\pm \text{SD}$)	ALS patients ($n=917$)	Controls ($n=2662$)	p-Valuea
${\mathrm{PM}}_{10}$, ${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$	$31.8\pm 1.4$	$31.6\pm 1.2$	$<0.001$
${\mathrm{PM}}_{\text{coarse}}$, ${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$	$10.4\pm 0.7$	$10.3\pm 0.6$	$<0.001$
${\mathrm{PM}}_{2.5}$, ${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$	$21.3\pm 0.9$	$21.2\pm 0.8$	0.08
${\mathrm{PM}}_{2.5}$ absorbance, ${10}^{-5}/\mathrm{m}$	$1.43\pm 0.20$	$1.40\pm 0.18$	$<0.001$
${\text{NO}}_2$, ${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$	$26.9\pm 5.6$	$26.0\pm 5.2$	$<0.001$
${\text{NO}}_{\mathrm{x}}$, ${\mathrm{\mu }\mathrm{g}/\mathrm{m}}^3$	$44.7\pm 9.6$	$43.6\pm 8.9$	0.002

Note: Annual air pollution exposure was assessed from 1992 to the date of enrollment in the study, and subsequently averaged for each participant; ALS, amyotrophic lateral sclerosis.

^ap-Value was calculated using an independent samples t-test.