Detecting community response to water quality violations using bottled water sales

New Research In

Edited by Arun Agrawal, University of Michigan, Ann Arbor, MI, and approved August 28, 2019 (received for review March 28, 2019)

Table 1.

Public notification requirements for Tier 1 and Tier 2 violations

Violation tier	Deadline for first notice	Repeat notices	Delivery modes	Contaminants
1	24 h	As directed by primacy agency	Broadcast media (radio, television)	Fecal coliform, E. coli^*
			Hand delivery	Turbidity^†
			Posting in conspicuous locations	Nitrate, nitrite^‡
			Other methods approved by state
2	30 d	Every 3 mo	Mail	All other MCL, MRDL, TT violations^§
			Hand delivery
			Other methods approved by state

↵* Fecal coliform and total coliform are regulated under the Total Coliform Rule. Tier 1 violations are triggered by an MCL violation or failure to test for fecal coliform after a repeat sample tests positive for total coliform.
↵^† Turbidity is sampled as an indicator of microbial concerns under the Groundwater Rule and rules related to surface water treatment. A Tier 1 violation can occur due to MCL exceedance or failure to consult with primacy agency within 24 h of MCL exceedance. Elevated levels of turbidity can interfere with disinfection and promote growth of bacteria, viruses, and parasites (e.g., Cryptosporidium).
↵^‡ Nitrate and nitrite are regulated under the Phase II Rule. A Tier 1 violation can occur due to MCL exceedance or failure to take confirmation sample within 24 h of MCL exceedance.
↵^§ Tier 2 violations occur when water systems do not comply with other requirements related to MCL, maximum residual disinfectant level (MRDL), and treatment technique (TT).

Table 2.

Estimated effects of quality violations on bottled water sales

Coefficient estimates of β₁ in Eq. 1, for 6 models. For model 1, the estimate represents the average percent change in sales associated with any type of Tier 1 violation; ***significant at the 1% level; *significant at the 10% level. SEs (in parentheses) clustered at county level. All regressions include year, week, and county fixed effects. In addition, regressions control for all variables presented in Eq. 1.

Table 3.

Estimated effects of quality violations on bottled water sales, by demographic groups

Coefficient estimates of β₁ in Eq. 1, for 4 types of communities, described in SI Appendix, SI Materials and Methods; ***significant at the 1% level; **significant at the 5% level. SEs (in parentheses) clustered at county level. All regressions include year, week, and county fixed effects. In addition, regressions control for all variables presented in Eq. 1. Counties are designated as low-income if household income is below the median of the sample, based on the average income across all years for each county. Counties are classified as rural if average housing density across all years is <16 units per square mile, based on rural categories defined in ref. 22.