The US Court of Appeals for the District of Columbia Circuit ruled Tuesday that the Environmental Protection Agency (EPA) should take into account pulp mill toxins such as mercury, dioxin and more in setting emissions standards.

The lawsuit between the Louisiana Environmental Action Network and the EPA was hinged primarily on whether it was “necessary” for the EPA to calculate the emission limits for such toxins and thus revise the emission standard that they first released in 2001. The EPA is required under the Clean Air Act to conduct such emission standard reviews every eight years, and the EPA did not consider these pulp mill toxins in 2001, or in any review since. They argued that, since they were only required to consider those toxins assessed in the initial review, and assessing any additional toxins was optional. In the most recent review, the EPA stated that it decided not to review the additional pollutants due to time constraints that left it unable to collect sufficient information for calibrating the proper limits.

The court, however, ruled that the Clean Air Act requires emissions standards for each source category every eight years, and this means that the EPA must address all of the listed air toxics of a source category. In this case, the EPA failed to do so in its most recent 2017 review. Based on this holding, the court directed the EPA to set limits on the listed air toxics that pulp mill combustion sources are known to emit.