Table 3.

Concentrations (Geometric Mean) and Detection Frequencies of Five Organophosphate Pesticides Most Commonly Detected in Vehicle Dust in Lower Yakima Valley, WA. Farmworker (FW) and nonfarmworker (NFW) vehicle dust concentrations are in units of nmol OP/ gram house dust.

OP Pesticide	Thinning Season				Non-spray Season
	Geometric				Geometric
Azinphos-methyl	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI
FW	89	99%	3.304**	(0.181–60.222)	65	60%	0.064**	(0.001–27.459)
NFW	84	79%	0.206	(0.007–6.995)	70	40%	0.009	(0.001–4.553)
	Geometric				Geometric
Malathion	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI
FW	89	91%	0.306**	(0.008–11.378)	65	15%	0.008**	(0.001–0.650)
NFW	84	56%	0.025	(0.001–1.332)	70	14%	0.003	(0.001–1.055)
	Geometric				Geometric
Phosmet	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI
FW	89	98%	0.523**	(0.047–5.861)	65	38%	0.053*	(0.001–33.634)
NFW	84	80%	0.101	(0.007–1.541)	70	14%	0.010	(0.001–1.279)
	Geometric				Geometric
Chlorpyrifos	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI
FW	89	70%	0.099**	(0.001–6.885)	65	65%	0.001	(0.001–0.519)
NFW	84	36%	0.009	(0.001–1.179)	70	41%	0.001	(0.001–0.584)
	Geometric				Geometric
Diazinon	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI
FW	89	55%	0.014**	(0.002–0.081)	65	34%	0.005*	(0.001–0.054)
NFW	84	36%	0.007	(0.001–0.103)	70	27%	0.003	(0.001–0.047)

^“**”indicates significant difference at p<0.001 and

^“*”at p<0.05 between FW and NFW, based on Welch two-sample ttests.