Table 2.

Exposure prevalence in 405 childhood acute lymphoblastic leukemia cases and 2,080 age-matched controls across exposure windows, metrics, and buffer sizes.

Exposure metric and buffer size	Primary window		Perinatal window
	Cases ($n=405$)	Controls ($n=\mathrm{2,080}$)	Cases ($n=405$)	Controls ($n=\mathrm{2,080}$)
	n (%)	n (%)	n (%)	n (%)
${\text{ID}}^2\mathrm{W}$ $2\mathrm{km}$
Exposed	14 (3)	37 (2)	7 (2)	13 (1)
Unexposed	391 (97)	2,043 (98)	398 (98)	2,067 (99)
${\text{ID}}^2\mathrm{W}$ $5\mathrm{km}$
Exposed	31 (8)	122 (6)	18 (4)	61 (3)
Unexposed	374 (92)	1,958 (94)	387 (96)	2,019 (97)
${\text{ID}}^2\mathrm{W}$ $10\mathrm{km}$
Exposed	59 (15)	270 (13)	41 (10)	153 (7)
Unexposed	346 (85)	1,810 (87)	364 (89)	1,927 (83)
${\text{ID}}_{\text{ups}}$ $2\mathrm{km}$
Exposed	6 (2)	16 (1)	3 (1)	5 (1)
Unexposed	399 (98)	2,064 (99)	402 (99)	2,075 (99)
${\text{ID}}_{\text{ups}}$ $5\mathrm{km}$
Exposed	12 (3)	43 (2)	6 (1)	21 (1)
Unexposed	393 (97)	2,037 (98)	399 (99)	2,059 (99)
${\text{ID}}_{\text{ups}}$ $10\mathrm{km}$
Exposed	18 (5)	74 (4)	12 (3)	39 (2)
Unexposed	346 (95)	1,810 (96)	393 (97)	2,041 (98)

Note: Exposure for each buffer size and metric was dichotomized due to low exposure prevalence. ${\text{ID}}^2\mathrm{W}$, inverse distance-squared weighted well count; ${\text{ID}}_{\text{ups}}$, inverse distance to the nearest upgradient UOG well; UOG, unconventional oil and gas.