Table 2.

Parameter values for α, which describes the proportional change in the rate ratio of each WSH-attributable disease associated with a 1°C increase in surface temperature. α values are derived from a literature review and meta-analysis described in the Supplementary Information. (Modified from prior work⁶.)

Disease		Water and sanitation access scenarioa	α value (95% CI)
Diarrheal diseases	II	Centralized, treated drinking water is piped to each residence AND improved sanitation facilities are appropriately installedb,c	0.077 (0.046, 0.108)
	IV	Drinking water is available from centralized piped systems, but treatment is incomplete or nonexistent (partially improved) AND improved sanitation facilities are appropriately installedb,c	0.080 (0.070, 0.090)
	V	Either improved sanitation facilities or partially improved drinking water is availableb,c,d	0.030 (0.012, 0.050)
	VI	No improved or partially improved drinking water or improved sanitation is availableb,c	0.056 (0.034, 0.078)
	Aggregate		0.063 (0.039, 0.086)
Malaria			0.125 (0.023, 0.227)
Dengue fever			0.260 (−0.052, 0.572)
Japanese encephalitis			0.079 (0.033, 0.126)

^aBecause baseline diarrhea risk and the impact of temperature on disease risk may depend on local conditions, α values for diarrheal diseases are shown for specific water and sanitation access scenarios as well as aggregated across all scenarios. Scenario-specific baseline rate ratios were obtained from prior work⁶: II = 2.5; IV = 4.5; V = 5.2; and VI = 11.2, using an idealized scenario with no transmission of diarrheal diseases from unsafe water or sanitation as the reference group.

^bImproved sanitation includes a sewer connection (typically seen in urban areas), a triple compartment septic tank, an anaerobic biogas digester, a double barrel funnel type septic tank, and a urine-separating toilet with a septic tank. The latter four designs, found in rural areas, reduce pathogen loads through extended residence times as well as physical and chemical inactivation of pathogens, depending on soil and weather conditions. Unimproved sanitation includes unprotected stool pits and the absence of any sanitation system.

^cImproved drinking water is defined as water that comes from centralized piped water systems that are treated regularly. Partially improved drinking water also comes from centralized piped water systems, but treatment is irregular or nonexistent. Untreated wells and surface water sources were classified as unimproved.

^dCombined scenarios Va and Vb⁶; see Supplementary Methods.