Table 2. Comparison of demographic and exposure characteristics of applicators and non-applicators in 2005 (n = 79), and 2009 (n = 41).

Characteristics	2005		2009		P-value
	Non-applicators (n = 38) Mean (SD)	Applicators (n = 41) Mean (SD)	Non-applicators (n = 20) Mean (SD)	Applicators (n = 21) Mean (SD)	Cohorta	Job categoryb	Interactionc
Age (y)	15.4 (1.7)	15.2 (1.7)	15.5 (1.5)	15.5 (2.1)	0.6	0.8	0.8
Education (y)	7.8 (3.8)	6.8 (4.2)	9.5 (1.5)	9.3 (1.5)	< 0.001	0.2	0.4
Days worked		22.4 (6.9)		18.9 (7.4)	0.08
Years worked		5.5 (2.3)		2.1 (1.0)	< 0.001

^a, comparison between 2005 and 2009 cohorts

^b, comparison between applicators and non-applicators across the two years of the study

^c, Interaction between job category and cohort