The four facilities subject to EPA’s 2002 National Emissions Standards for Hazardous Air Pollutants (NESHAP) for leather finishing operations received a clean bill of health following the Agency’s residual risk and technology review (RTR).
Specifically, the RTR found that the risks to human health and the environment from hazardous air pollutants (HAPs) emitted by the facilities are acceptable and that there are no new pollution control technologies that are economically feasible for the facilities. Accordingly, the EPA is proposing no changes to the HAP numerical emissions limits included in the 2002 NESHAP. The proposal does include several potential amendments addressing startup, shutdown, and malfunction (SSM); performance testing; recordkeeping; and reporting.
Sources and Limits
The 2002 NESHAP defines leather finishing as “a single process or group of processes used to adjust and improve the physical and aesthetic characteristics of the leather surface through the multistage application of a coating comprised of dyes, pigments, film-forming materials, and performance modifiers dissolved or suspended in liquid carriers.”
Emissions of HAPs occur from volatilization during the application of the coating, drying, or curing of the coating and from handling, storage, and cleanup of the finishing materials. Wastewaters laden with HAPs are also a potential source of emissions at facilities that use water curtains and water baths for particulate control. The emissions point types associated with these emissions sources include process vents, storage vessels, wastewater, and fugitive sources.
The NESHAP limits emissions from new and existing leather finishing operations are expressed as total HAP emissions per 1,000 square feet of leather processed over a rolling 12-month compliance period. Sources must record the mass of HAPs in coatings applied to the leather either through an inventory mass balance or measure-as-applied approach.
HAP emissions from the source category include propyl cellosolve, glycol ethers, diethylene glycol monobutyl ether, trimethylamine, diethylene glycol monomethyl ether, ethylene glycol, toluene, methyl isobutyl ketone, and chromium (III) compounds.
Risks are Acceptable
The residual risk portion of the RTR is based on minimum protective levels for individual and populationwide cancer risks as well as chronic and acute noncancer health risks and risks to the environment. For example, a cancer risk for individuals of 100 in 1 million is the presumptive upper limit of acceptable risk. Based on its review, the EPA found that the cancer risks to the individual most exposed is below 1 in 1 million from both actual and allowable emissions. The risks of acute and chronic noncancer human illness as well as risks to the environment also met the Clean Air Act (CAA) requirement that the NESHAP protect public health and the environment with an ample margin of safety.
Controls Not Cost-Effective
The technology portion of the RTR identified two technically feasible control technologies—biological treatment, whereby microbes consume organic pollutants into food and convert them into water and carbon dioxide; and concentrators, which use adsorbents to remove organic pollutants from an exhaust stream. Based on the high cost of each ton of HAPs removed, the EPA did not find that either technology was cost-effective for removing HAPs from leather finishing operations.
The proposal includes these additional actions:
- SSM. The proposal would align the leather finishing NESHAP with requirements for SSM as clarified by the D.C. Circuit in Sierra Club v. EPA; that is, the standards must be met at all times, including during SSM. Malfunction applies to air pollution control equipment. The EPA notes that none of the four facilities use pollution control equipment; therefore, there can be no instance where such equipment malfunctions.
- Performance testing. Performance testing applies to air pollution control equipment. Again, since the facilities have no such equipment, there can be no performance test. The EPA is, nonetheless, proposing a requirement that the facility owner or operator record the process information necessary to document operating conditions during the test and include in such records an explanation to support that such conditions represent normal operation.
- Recordkeeping. The proposal would revise the deviation notification report to include two new reporting elements—an estimate of the quantity of HAPs emitted during the 12-month period of the report in excess of the standard and the cause of the events that resulted in the deviation from the standard (including unknown cause, if applicable).
The EPA notes that it found 24 facilities with leather finishing operations, but only four of these—three in the Northeast, one in Minnesota—are major sources subject to the NESHAP; the remaining 20 are area sources.
The proposal was published in the March 14, 2018, Federal Register (FR).