Dose Response. 2013 May 16;11:517-42.

EPA’s Stage 2 Disinfection Byproducts Rules (DBPR) and Northern Kentucky Water: An Economic and Scientific Review.

Henry H

Department of Physics, Northern Kentucky University, Nunn Drive, Highland Heights, KY 41009, USA


Implementation of EPA’s Stage 2 Disinfection Byproducts Rules (DBPR) in Northern Kentucky will cause a water rate increase of over 25%. Hence a review was undertaken, considering both economics and science in the context of President Obama’s 2009 scientific integrity directive. The rules purport to avoid up to 0.49% of new bladder cancers by reducing the levels of DBPs in drinking water – a benefit so small that failure to implement will not cause unreasonable risk to health (URTH). It suggests at most one Northern Kentucky death avoided over 17 years for a cost of $136,000,000 ($1700 per household). Even this small benefit is probably overstated. EPA finds no “causal link” between DBPs and bladder cancer, and EPA acknowledges problems with the epidemiological data used in their calculation: the data appear contradictory and inconsistent, may be skewed toward “positive” results, and suggest different cancer sites than animal studies. Two similar international agencies disagree with EPA’s conclusions. The science is based on the Linear No Threshold (LNT) dose response model for DBPs, but this may not be the correct model. 83% of EPA’s epidemiological data show a statistical possibility that low levels of DBPs might be beneficial or have no effect.

KEYWORDS: Chlorinated Drinking water, Disinfection byproducts (DBP), EPA Water Regulations, Hormesis, LNT model, Trihalomethane (THM)

PMID: 24298228



Implementation of the 1974 Safe Drinking Water Act (SDWA) in the United States has led to a much healthier environment.

But after 40 years of clean water regulations, does the cost to remove smaller and smaller amounts of contaminants outweigh possible additional health benefits? This analysis suggests the answer is “YES” in regard to EPA’s Stage 2 Disinfection Byproducts Rules (DBPR).

Stage 2 DBPR mandates reduction of the percentages of nine chemicals found in chlorinated drinking water as disinfection byproducts (DBPs) of the chlorination process. Although DBP levels are already extremely low (less than 0.14 parts per million or 0.000014%), Stage 2 DBPR proposes to take them lower.

EPA acknowledges there may be no health benefit whatsoever from these new rules; and the maximum possible estimated benefit is so small it is impossible to measure.

Yet the extremely high cost to implement these rules is causing a 25% water rate increase in the Northern Kentucky Water District (NKWD), Kentucky’s largest water district.

Questionable Health Benefit

EPA makes an “upper bound” estimate that Stage 2 DBPR will avoid up to 0.49% of new bladder cancers (1). Yet since no “causal link” has been found between DBPs and bladder cancer (1) EPA acknowledges the benefit “could be zero” (2); ie, no cancers may be avoided.

EPA nevertheless believes the epidemiological data suggest a “potential hazard concern” (1), and they wish to be proactive in case later studies find a causal link. But this conservative attitude can be taken too far if the cost is high and the epidemiological evidence is weak.

With this in mind, EPA analyzed the data to maximize their estimate of the cancer risk – and hence the estimated cancers avoided by reducing DBP levels. Yet such an aggressive analysis generated a substantial overstatement of the risk:

  1. It is questionable if the epidemiological data which underpins Stage 2 DBPR can be used to draw accurate conclusions.
    1. EPA acknowledged that the results of seven epidemiological studies used to estimate risk “have been mixed” (1) and inconclusive. The author of four of the studies expressed concern about “internal consistency, as well as consistency with other findings” (3).
    2. Two similar international agencies – the International Agency for Research on Cancer (IARC) and the International Programme on Chemical Safety (IPCS) – also pointed out data inconsistencies. As a result, IARC and IPCS found inadequate or insufficient evidence for EPA’s conclusions that chlorinated drinking water causes bladder cancer.
  2. 83% of the epidemiological studies used by EPA showed that chlorinated drinking water might have no effect on bladder cancer risk or even decrease the risk (2). However, EPA’s risk analysis rejected all data which failed to show a positive correlation between chlorinated water and cancer – yet accepted all positive data. This was done without adequate justification, and the result was to increase the risk estimate by slanting the analysis toward a positive correlation.
  3. “EPA assumes there is a linear relationship between average DBP concentration and relative risk of bladder cancer  . . . [and further] that there is no threshold below which there is no risk” (2). However, there are sound scientific reasons to question this Linear No Threshold (LNT) approach to risk with low-level DBPs:
    1. A comprehensive 2013 study showed that the LNT model made consistently poor predictions in the low-dose region.
    2. At least one DBP has been shown not to follow LNT; it is safe below a certain threshold. The other eight DBPs have not been studied fully enough to make a low dose conclusion.
    3. The essence of LNT is to extrapolate high dose studies to low doses. However, high doses of DBPs in animal studies have suggested liver and kidney cancer – not bladder cancer. In 1993 EPA’s Scientific Advisory Board stated this discrepancy “must be resolved if [EPA] is to develop a scientific basis for a disinfection rule” (4); yet this still has not been resolved.

In summary, EPA’s estimate that Stage 2 DBPR will avoid up to 0.49% of new bladder cancer cases is not justified by the evidence. Instead, the maximum risk is substantially lower – or even zero. Some data even suggest low level DBPs may be beneficial to health and/or longevity.

Cost Far Outweighs Maximum Possible Savings

It will cost NKWD customers $8,000,000 per year to implement Stage 2 DBPR – spread among 80,000 households with 300,000 people.  Avoiding  0.49% of new bladder cancers represents about 0.3 bladder cancers per year and would save treatment costs of about $42,000 (based on national averages). Hence the graph illustrates the best case financial cost-benefit scenario:

EPAStage2DBPRCostBenefitBladder cancer is a horrible disease; and although 4 out of 5 cases are cured, one must have great sympathy for those afflicted and their families. Nevertheless, this is a large unfunded mandate to place on NKWD customers for so little possible health or financial benefit.

In situations like this with an unfavorable cost-benefit ratio, EPA often applies a standard called Unreasonable Risk to Health (URTH) as a basis for relief from its rules. According to EPA’s criteria, there is no URTH if Stage 2 DBPR is not implemented.


Based on the NKWD situation, there seems no justification to implement EPA’s Stage 2 DBPR.

Details and complete references are found in the full article, which is available free of charge at: .


  1. USEPA (U.S. Environmental Protection Agency). 2006. National Primary Drinking Water Regulations: Stage 2 Disinfectants and Disinfection Byproducts Rule, Final Rule, Federal Register 71:2.
  2. USEPA (U.S. Environmental Protection Agency). 2005. Economic Analysis for the Final Stage 2 Disinfectants Byproducts Rule. EPA 815-R-05-010.
  3. Cantor KP et al. 1998. Drinking Water Source and Chlorination Byproducts Risk of Bladder Cancer. Epidemiology 9, 1:21-28.
  4. USEPA SAB (U.S. Environmental Protection Agency Scientific Advisory Board). 1993. EPA-SAB-DWC-COM-94-002.



Hugh Henry, Ph.D.

Department of Physics, Northern Kentucky University

Nunn Drive, Highland Heights, KY 41099

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