Table 2.

Comparison of participant recall proximity to farmland and satellite-derived proximity to farmland: five categories of proximity to farmland by case–control status and by calendar years of residence (1978/2001).

	Participant recall: proximity to farmland					% match	Kweighted	Spearman
	On a farm	<1/4 mile	1/4–1 mile	1–5 miles	>5 miles
Using satellite-derived land cover information: proximity to farmland Cases, 1978 (N = 184)
On a farm	5	5	1	1	0	19	0.38*	0.52*
<1/4 mile	4	13	10	15	16
1/4–1 mile	0	2	6	21	31
1–5 miles	0	0	2	11	32
>5 m iles	0	0	0	0	0
Cases, 2001 (N = 184)
On a farm	9	7	2	1	1	26	0.50*	0.70*
<1/4 mile	2	15	10	6	1
1/4–1 mile	0	0	8	26	10
1–5 miles	0	1	3	15	58
>5 m iles	0	0	0	0	0
Controls, 1978 (N = 347)
On a farm	12	15	6	1	0	20	0.40*	0.55*
<1/4 mile	10	28	16	18	15
1/4–1 mile	3	4	12	46	60
1–5 miles	0	3	0	17	66
>5 m iles	0	0	0	0	0
Controls 2001 (N = 347)
On a farm	20	9	8	2	0	27	0.50*	0.68*
<1/4 mile	6	34	24	21	2
1/4–1 mile	1	8	8	35	30
1–5 miles	0	2	0	33	93
>5 m iles	0	0	0	0	0

^*P<0.0001.