National Park Service Oral Comments on EPA Proposal for 

Secondary National Ambient Air Quality Standard for Oxides of Nitrogen and Sulfur

August 25, 2011

1) The National Park Service (NPS) commends EPA’s innovative approach to define 

ecologically-relevant secondary standards for oxides of nitrogen and sulfur. The Aquatic 

Acidification Index eloquently links ambient atmospheric concentrations to deposition to 

ecological impacts. We agree with the Clean Air Science Advisory Committee that the 

scientific basis of the Aquatic Acidification Index is sound and well supported. 

2) NPS disagrees with EPA’s decision not to set separate secondary standards for NOx and 

SOx at this time. We believe that the risks of not acting far outweigh the risks of 

proceeding while some uncertainties remain.

3) EPA has clearly demonstrated that the current secondary standards are inadequate to 

protect sensitive resources. EPA has also clearly demonstrated that resources are being 

adversely impacted at current levels of deposition and that additional reductions in levels of 

deposition are needed.

4) Our national parks encompass some of the most acid-sensitive ecosystems in the country. 

The Aquatic Acidification Index is appropriate to address impacts for these sensitive 

ecosystems, such as those in Shenandoah and Great Smoky Mountains National Parks. We 

encourage EPA to set secondary standards now to protect these sensitive ecosystems. 

5) We disagree with EPA’s assertion that uncertainties prevent EPA from understanding the 

level of protection afforded by a specific level and form of the standard. For example, EPA 

cites the lack of monitoring data in the western states as an uncertainty, yet EPA has set 

primary standards for ozone, PM, NO2, and SO2, despite a lack of monitoring data to 

adequately describe the spatial variability in the West for these pollutants. 

6) EPA cites the need for additional atmospheric and water quality monitoring and proposes a 

pilot program to address data gaps. Yet EPA has not identified funding for the proposed 

pilot program, and it will be 2012 before a plan for such a pilot program is even designed. 

We strongly encourage EPA to demonstrate their commitment to follow through by clearly 

identifying the needed funding for this effort. 

7) The pilot program described in the Federal Register focuses on monitoring to improve the 

characterization of SO2, particle SO4, and NOy. NPS agrees with the need to evaluate 

methods and would like to participate with EPA in this effort. We encourage EPA to 

include ecologists in the selection of areas for the pilot program. 

8) Funding and program planning are also needed to implement further water quality 

monitoring to define the spatial extent of acidified lakes and streams. This has been a need 

since the original NAPAP assessment was completed in 1990. Without a regulatory 

requirement, this monitoring has not been a funding priority. Setting separate, deposition-
based secondary standards now increases the imperative to commit the required funding to 

better characterize ecosystem sensitivity. 

9) Implementation challenges are real, but it is not appropriate to delay setting new secondary 

standards until these challenges are resolved. Because EPA can provide states greater 

flexibility in attaining the secondary standard, we believe that EPA can set new secondary 

standards concurrent to resolving uncertainties without imposing undue burden to the 

States and the regulated community. Establishing the secondary standard now will 

demonstrate EPA’s commitment to protecting ecosystems that are known to be adversely 

affected by deposition of NOx and SOx and will allow states to begin planning for 

attainment in the context of other ongoing regulatory efforts.

10) The one-hour primary standards for NO2 and SO2 are not ecologically relevant to protect 

sensitive ecosystems. EPA has not provided evidence that the reductions necessary to 

attain the one-hour standard would provide reductions in deposition at sensitive receptors. 

It would be preferable to set deposition-based standards and refine them as better 

information becomes available than to adopt secondary standards that are not relevant for 

ecosystems. 

11) NPS will be submitting detailed written comments prior to the close of the public comment 

period.