Relative risks in 2×2×2 tables, as used in tables 2 and 4

Separate condensed tables of hazard distances are assembled for birth and death addresses, each showing near and far classes for hazard-Y and hazard-X, as below. (0.5 km in example)
		Birth addresses				Death addresses
		Hazard-X				Hazard-X
		Near	Far			Near	Far
Hazard-Y	Near	a	b	Hazard-Y	Near	e	f
	Far	c	d		Far	g	h
Example
		Bus station				Bus station
		⩽0.5	>0.5			⩽0.5	>0.5
BUT	⩽0.5	184	1224	BUT	⩽0.5	18	689
	>0.5	162	3558		>0.5	43	4378

Odds ratios serve here as estimators of the relative risks (RR) of birth proximities. ORs for different situations are listed below

	Example
	OR	(CI)*
*Confidence intervals calculated as suggested by Bland and Altman.²²
1 OR for nearY in absence of nearX = bh/df	2.19	(1.97 to 2.42)
2 OR for nearY in presence of nearX = ag/ce	2.71	(1.51 to 4.89)
3 OR for nearX in absence of nearY = ch/dg	4.64	(3.30 to 6.51)
4 OR for nearX in presence of nearY = af/be	5.75	(3.52 to 9.42)
5 OR for nearY+nearX v neither = ah/de	12.58	(7.74 to 20.45)
6 OR for nearY overall = {(a+b)(g+h)}/{(c+d)(e+f)}	2.37	(2.14 to 2.62)
7 OR for nearX overall = {(a+c)(f+h)}/{(b+d)(e+g)}	6.01	(4.56 to 7.91)

In the example, both exposures are active (OR = 2.19, 4.64) when outside the effective range of the other; and each is increased (2.71, 5.75) when within range of the other. Finally, comparing double proximities with double non-proximities, the OR for a double exposure is 12.58.