Others are commenting on the Los Angeles Times article by Ralph Vartabedian titled “How Environmentalists Lost the Battle Over TCE.”
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A few details may be helpful for understanding the jargon. The federal Maximum Contaminant Level (MCL) for TCE is 5 parts per billion (ppb). Virtually all public water suppliers must achieve this standard in finished water, and the standard itself is an applicable cleanup standard for soil and water remediation.
In a short commentary on the Los Angeles Times article, the editors wrote:
If someone started their [sic] education about TCE in drinking water with this article, they might think that TCE is currently unregulated. In fact, 100s if not 1000s of drinking water wells have been impacted, taken out of service or treated because of the 5 ppb MCL that has been in effect for years. In addition, there has been extensive remediation efforts on groundwater contamination sites. It is not clear how dramatic the impact would be if a new risk assessment resulted in a lower MCL (e.g. 1 ppb).
Presumably, the McGuire editors mean to suggest that a lower MCL might not have a dramatic impact on the level of TCE permitted; after all, the suggested difference is only a factor of five. However, the economic implications of such a change are likely to be quite dramatic. In general, the marginal cost of achieving any enforceable standard rises with the stringency of the standard. As the standard approaches zero, the marginal cost rises exponentially. The marginal cost of achieving zero may be infinite, meaning that it cannot be achieved at any price.