The Kentucky Division for Air Quality (KDAQ) regulates potentially hazardous matter or toxic substances (commonly referred to as toxic air pollutants or “TAPs”) through 401 KAR 63:020. This regulation applies to each affected facility that emits or may emit TAPs, unless the emissions are otherwise regulated under Kentucky Administrative Regulation. The air toxics regulation, 401 KAR 63:020, may look short and unassuming but it can be deceptively complex. There is no mention of specific emission limits or control requirements, the regulation simply states: 

Persons responsible for a source from which hazardous matter or toxic substances may be emitted shall provide the utmost care and consideration, in the handling of these materials, to the potentially harmful effects of the emissions resulting from such activities. No owner or operator shall allow any affected facility to emit potentially hazardous matter or toxic substances in such quantities or duration as to be harmful to the health and welfare of humans, animals and plants. Evaluation of such facilities as to adequacy of controls and/or procedures and emission potential will be made on an individual basis by the cabinet.

But besides the common sense work practice of handling toxic substances carefully, what does this actually mean for you? The key phrase is the last sentence. The cabinet (i.e., KDAQ) assesses the adequacy of controls and procedures as well as the potential toxic emissions on a case-by-case basis. These requirements depend on various factors, including the TAP emission rates, emissions source characteristics, and the proximity of major emission points to sensitive locations, as well as the proper use of the latest air quality dispersion modeling systems (i.e., AERMOD and AERSCREEN). 

For many subject sources, submitting emissions calculations of potentially hazardous matter and toxic substances and abiding by the work practice requirements of 401 KAR 63:020 is sufficient. KDAQ will perform screening level air dispersion modeling with the potential emissions of TAPs and compare the results to the EPA Regional Screening Levels (RSLs) for carcinogenic and non-carcinogenic risk. The RSLs are frequently updated with the latest toxicological data and determinations. The latest RSLs (last revised June 2017) can be found here

If the source's modeled TAP emissions remain below the RSLs (1 in a million for carcinogens and 1.0 hazard quotient for non-carcinogenic compounds), the source is in compliance with 401 KAR 63:020 as long as the source does not alter process rates, material formulations, or any other factor that would result in an increase of hazardous or toxic emissions. The associated air permit will often list as the compliance demonstration method that the affected emission unit is in compliance with 401 KAR 63:020 based on the emission rates of toxics and hazardous air pollutants given in the application and supplemental information submitted by the source. 

If the source's modeled TAP emissions exceed the RSLs, there is a wide range of requests KDAQ can make. The requests generally come in the form of a Notice of Deficiency (NOD) in response to the permit application triggering 401 KAR 63:020 review. Possible requests include that a source refine their potential TAP emissions factors, which are often initially calculated as a conservative worst-case mix, or remodel the TAP emission factors using a more intricate air dispersion model (i.e., AERMOD). If subsequent refinements cannot demonstrate acceptable risk, KDAQ has two basic options: 1) scale your emissions rates to the point that offsite impacts are acceptable by establishing a synthetic emissions limitation in your permit, or 2) request that the applicant perform a Toxic Air Pollutant - Best Available Control Technology (TAP-BACT) analysis. Options to implement TAP-BACT include: 1) installing a control technology, 2) proposing an operational limit, 3) reformulating as to alleviate the ambient impact of the pollutant, 4) performing a risk assessment demonstrating a negligible human health impact, or 5) proposing an alternative solution to resolve the carcinogenic or non-carcinogenic health impacts. The path for resolution of a TAP emissions exceedance should also be evaluated on a case-by-case basis as a single solution might not be the most effective for every situation. 

To learn more about the potential impact to your facility or for assistance navigating TAP compliance matters, call Larissa Rückl (859-341-8100 x112) or Mike Zimmer (859-341-8100 x103) in our Covington Office.