Publication / Inside EPA
February 12, 2014
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Early EPA Analysis Suggests Strict New Water Quality Criteria For Aluminum

EPA’s early analysis on the adverse effects of aluminum shows the metal is significantly more harmful to some mussel species than previously estimated, a finding that suggests that the agency’s ongoing effort to revise its water quality criteria will result in strict new limits and force some states to adopt new approaches to regulate the substance.

The agency is also gathering additional data from outside experts — expected in the coming months — on the metals’ toxicity to mussels and effects on a host of other species to ensure that any new criteria will be adequately protective of aquatic life.

“By spring 2014, EPA expects to receive additional data about pH interactions with aluminum toxicity across a range of species, as well as the results of mussel toxicity tests with aluminum. EPA will consider this information to ensure that the national 304(a) aluminum criteria update will be protective of all aquatic life, including mussels, at various pH and [water] hardness levels,” EPA Region III officials told West Virginia’s Department of Environmental Protection (WVDEP) late last month. Relevant documents are available on (Doc. ID: 2461044)

EPA added that information provided by the Fish and Wildlife Service (FWS) indicates that mussels may be “more sensitive to the effects of aluminum than other organisms for which EPA currently has data” and that “because of the concern on mussel sensitivity to aluminum, EPA will be looking for additional data to refine our estimates of aluminum toxicity to mussels.”

The agency’s comments came in a letter to WVDEP where officials all but rejected the state’s request to approve proposed new criteria for aluminum — which used an approach that EPA had already approved in Colorado and New Mexico. EPA Region III said an initial agency review of the scientific literature, as well as its consultation with the FWS, shows that West Virginia’s proposed standard would not likely protect mussel species.

Aluminum is a metal that is toxic to aquatic life in both its dissolved and solid states. It is naturally occurring but also is released into the environment from coal mining and finishing operations, coal-fired power plants, and waste water treatment plants, among other sources.

EPA’s current criteria — set in 1988 — measures aluminum in terms of total recoverable metal (TRM) in water based on an average pH scale. The agency set an acute criteria of 750 micrograms per liter (ug/L) and 87 ug/L for chronic exposures.

EPA and state regulators use such criteria — risk-based concentration limits — to craft enforceable limits in permits, water quality standards and other regulatory levels for limiting harms to aquatic species. Based on its current criteria,EPA says that 6,610 miles of rivers and streams are currently considered impaired because of excess levels of aluminum.

EPA limited its 1988 criteria to apply within the 6.5 to 9 pH range because it found that aluminum is “substantially less toxic at higher pH and hardness, but the effects of pH and hardness are not well quantified at this time.”

Despite its initial uncertainty over pH and hardness, over the past few years, EPA has approved new state criteria in New Mexico and Colorado that continue to account for pH as a factor in setting aluminum criteria but for the first time also considers water hardness as a factor. Industry and states have pushed such a standard, arguing it is a more precise method of measurement than the current recommendation, using EPA’s findings that aluminum tends to be less toxic in higher hardness levels as a basis.

Both states adopted criteria that use a sliding scale to determine aluminum limits on TRM in bodies of water based on waters’ hardness, resulting in criteria that are weaker than the agency’s 1998 limits.

Last year, West Virginia proposed an emergency rule that mirrored New Mexico’s criteria but only measured dissolved aluminum in the water column without accounting for solid forms of the substance. The state asked EPA to approve the criteria so that regulators could use it when setting permit limits and crafting other regulatory levels.

But in its letter to state officials, the agency says that data provided by FWS, together with some recent studies EPA has reviewed, shows that West Virginia’s proposed criteria may not adequately protect mussel species.

For example, a July 19 letter from FWS to Region III recommended that the agency not allow for consideration of hardness as a factor in setting concentration limits but that pH likely has an adverse effect. FWS concluded that based on studies it reviewed, “ambient pH had a significant effect on the accumulation in the [mussels’] gills, whereas the effect of the water hardness was only of minor importance,” concluding that “hardness should not be considered in setting the standard to protect mussels as it does not affect exposure in these filter feeders and would greatly increase the risk of take.”

EPA added that it recently became aware of another study that was conducted on mussels native to West Virginia “and corroborates the evidence from the mussel studies provided by [FWS].”

“EPA believes that these studies provide sufficient weight of evidence to indicate mussels may be more sensitive to aluminum exposure than other species in West Virginia’s data set,” the agency wrote, adding that West Virginia’s proposed revisions “do not take into account potential impacts on mussels and a rationale for the exclusion of these potential effects has not been provided.”

EPA said that protection of these resources “should be an important consideration in the derivation of any new water quality criteria for the protection of aquatic life in West Virginia.”

A WVDEP source believes that any new criteria EPA develops will now utilize pH scales to determine specific testing based on water acidity. “I think they are going to have pH as more of a limiting factor than how West Virginia put it or how other states put it . . . It may have various thresholds for different waters that have endangered fish and mussels,” the source says.

The source believes that any new criteria may follow the approach EPA recently adopted when it set new criteria for ammonia. In that case, the agency strengthened its criteria for ammonia based in large part on FWS data showing mussels’ heightened sensitivity to exposures.

The final ammonia criteria, which EPA unveiled in 2013, set strict new limits to protect mussels and other aquatic species but encouraged regulators to set site-specific criteria that could provide flexibility in cases where mussels may not be present.

One environmentalist suggests that EPA could also use an approach it used when setting criteria for copper in 2007. In that case, the agency used the so-called Biotic Ligand Model (BLM), a computer model that uses 10 water chemistry parameters to calculate a freshwater criterion. According to the source, BLM is beneficial in that it would better account for site-specific conditions when setting aluminum criterion — essentially setting localized standards for each body of water — but it’s much more cumbersome to operate than a singular standard because of it’s specificity. — Miranda Green