Regulatory Policy Implications of 1,4-Dioxane - Environmental Investigation and Remediation - page 456

A n o t h e r o b j e c t i o n t o f o l l o w i n g t h e p r e c a u t i o n a r y p r i n c i p l e a p p r o a c h t o r e g u l a t i n g e m e r g i n g
contaminants is that it is entirely possible that initial concerns over the potential environmental
harm or toxicity of a newly discovered contaminant in drinking water will not be substantiated by
later studies. This objection is not without foundation. After decades of spending millions of dollars
on remedial efforts to remove cis -1,2-dichloroethylene and trans -1,2-dichloroethylene * from ground-
water to comply with California maximum contaminant levels (MCLs) of 6 and 10 micrograms per
liter (μg/L), respectively, the California OEHHA drafted new Public Health Goals (PHGs) that
would revise the health criteria upward to 100 and 60 μg/L, respectively (Cal EPA, 2005). Many of
the groundwater cleanup sites, where millions of dollars have been expended, have concentrations
of these two isomers in the range between the current MCL and the proposed PHG.
The converse has also happened: in 2001, the California OEHHA revisited the PHG for perchloro-
ethylene, recommending a PHG of 0.06 μg/L. New i ndings of perchloroethylene health effects at
lower concentrations came about after decades of enforcement and compliance with the California
and federal perchloroethylene MCL of 5 μg/L. Similarly, USEPA Region 9 lowered the PRG for
TCE after taking into account the total exposure to its metabolic byproducts, haloacetic acids,
which also occur in drinking water treated by chlorination. The EEA report notes that the com-
monly feared risk of “false positives” occurs less often than the incidence of “false negatives”;
therefore, the precautionary principle is the road to follow into the future (EEA, 2000). Accordingly,
the precautionary principle is enshrined in the Treaty of the European Union.
10.1.1 E MERGING AND U NREGULATED C ONTAMINANTS
Emerging contaminants include chemical and microbial constituents that have not historically been
considered as contaminants but are present in the environment on a global scale. Broadly dei ned,
an emerging contaminant is a chemical or material that is characterized by a perceived, potential,
or real threat to human or ecological health but for which health standards have not yet been pub-
lished. Emerging contaminants by dei nition are not regulated. Once the presence and health threat
of an emerging contaminant such as 1,4-dioxane is recognized, it can take a decade or more before
a federal or state MCL is established, and then only if warranted in the judgment of USEPA and
state health agency professionals. The process for reviewing and adopting MCLs is discussed in
Chapter 6. Until federal or state agencies adopt an MCL, state health agencies often promulgate
interim guidelines for emerging contaminants (e.g., action levels, drinking water Guidelines, notii -
cation levels, PHGs, preliminary remediation goals, screening levels, and risk-based concentrations;
see Table 6.1). † Until regulators make a determination to adopt a standard or conclude that regulat-
ing an emerging contaminant is not warranted, ongoing exposure of unknown proportions and
unknown consequences may continue without regulatory intervention. Too often, the i rst indication
that a drinking water supply is threatened by a potentially toxic or carcinogenic agent is its detection
in the drinking water that is being served to and consumed by the public.
Under the status quo, the process for adopting regulatory standards requires a standard of proof
that involves a multiyear vetting process; this means that real harm may occur before action is
i nally taken to prevent further harm. In practice, harm or widespread evidence of environmental
contamination from a chemical used in industry seems to be a prerequisite for regulation, not unlike
the stop sign that is i nally erected at the intersection after a fatal accident occurs. In the case of
1,4-dioxane in groundwater, failure to test, regulate, and remediate 1,4-dioxane can mean that water
from production wells from which chlorinated solvents have been removed but in which 1,4-dioxane
remains is distributed to drinking water systems (e.g., the Bally, Pennsylvania, Superfund case). ‡
* cis -1,2-Dichloroethylene and trans -1,2-dichloroethylene are products of the biodegradation of trichloroethylene.
† The exception is Colorado, which has already adopted an MCL for 1,4-dioxane.
‡ See the USEPA website for the Bally, Pennsylvania Superfund site: http://www.epa.gov/reg3hwmd/super/sites/
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