Table 2.

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

OP Pesticide	Thinning Season				Harvest Season				Non-spray Season
	Geometric				Geometric				Geometric
Azinphosmethyl	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI
FW	85	99%	1.482**	(0.119–18.441)	82	98%	1.351**	(0.071–25.734)	78	95%	0.372**	(0.029–4.805)
NFW	86	79%	0.161	(0.007–3.992)	88	95%	0.301	(0.022–4.113)	79	65%	0.057	(0.002–2.124)
	Geometric				Geometric				Geometric
Malathion	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI
FW	85	88%	0.163**	(0.005–5.442)	82	80%	0.054*	(0.002–1.216)	78	62%	0.023**	(0.001–0.429)
NFW	86	72%	0.016	(0.006–0.538)	88	81%	0.031	(0.003–0.337)	79	54%	0.009	(0.001–0.161)
	Geometric				Geometric				Geometric
Phosmet	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI
FW	85	98%	0.556**	(0.031–10.116)	82	96%	1.057**	(0.032–29.972)	78	94%	0.282**	(0.029–2.783)
NFW	86	73%	0.046	(0.001–3.393)	88	97%	0.267	(0.019–3.733)	79	73%	0.043	(0.001–1.549)
	Geometric				Geometric				Geometric
Chlorpyrifos	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI
FW	85	60%	0.042**	(0.001–1.762)	82	49%	0.023**	(0.001–1.076)	78	47%	0.023**	(0.001–0.702)
NFW	86	29%	0.005	(0.001–0.460)	88	35%	0.007	(0.001–0.323)	79	27%	0.004	(<0.001–0.425)
	Geometric				Geometric				Geometric
Diazinon	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI	n	% Detect	Mean	95% CI
FW	85	73%	0.015*	(0.001–0.215)	82	93%	0.038	(0.003–0.478)	78	65%	0.013	(0.001–0.144)
NFW	86	72%	0.009	(0.001–0.237)	88	91%	0.034	(0.004–0.295)	79	66%	0.014	(0.001–0.174)

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

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