Note: Thank you to Jennifer Heathcote, RadTech’s Board of Directors’ Secretary, for collaborating on this issue’s column.
Metal Coatings Rulemaking and Win for Test Method
The South Coast Air Quality Management District (SCAQMD) board recently adopted amendments to the Metal Coatings Rule (Rule 1107). The rule regulates Volatile Organic Compound (VOC) emissions from metal coating operations and establishes VOC content limits for 22 coating categories, classified either as air-dried or baked, including several specialty and niche-use coatings. The amendments are in line with a regulatory trend to eliminate the use of tertiary-Butyl Acetate (t-BAc) and para-Chlorobenzotrifluoride (pCBtF), which were identified by California’s Office of Environmental and Health Hazard Assessment (OEHHA) as having toxic health endpoints, including carcinogenicity. The two compounds were exempted as VOCs in various rules and, according to the staff report, commonly are utilized by coating manufacturers to formulate SCAQMD-compliant coatings. While t-BAc currently is not considered exempt for metal coatings applications, pCBtF is exempt from the definition of VOC for all uses, including products regulated under Rule 1107. The rule changes will phase out pCBtF and t-BAc.
The district is allowing a five-year reformulation period for coating categories that currently lack viable alternatives, with one additional year provided for military specification and camouflage coatings due to their unique performance requirements. Colorants also are provided a five-year reformulation period to address unique reformulation challenges. Following the reformulation period, there is a one-year sell-through period and a two-year use-through period. After the phase-out period provided, Rule 1107 coatings would be prohibited from containing pCBtF and/or t-BAc in excess of 0.01 percent by weight.
RadTech initially had been strongly opposed to the proposal and asked for a full exemption from the rule. While RadTech did not get the exemption, the staff made various concessions that are very beneficial to the industry:
- No additional recordkeeping requirements.
- Added clarification in the staff report regarding testing of thin-film materials, which now reads: “South Coast AQMD understands that the lack of an approved test method for thin-film UV/EB/LED coatings creates compliance challenges. In these cases, manufacturers may rely on formulation data and ASTM D7767 to determine product VOC content for labeling purposes, consistent with existing regulatory practices.”
- To address RadTech’s concern about manufacturers being able to access the district’s position regarding determining VOC content for labeling, the agency committed to updating its VOC rules webpage to include clarification language regarding testing of thin-film energy-curable materials. This would make it more accessible to users and broaden the applicability beyond metal coatings.
- During the hearing, the chief enforcement officer essentially stated that the inspectors would be made aware of the test method allowance to prevent confusion that could potentially lead to legal liability for industry.
Staff stated they have made concessions for manufacturers to use ASTM D7767-11 as they believe it “…serves a good function.” The biggest win was that the test method guidance being provided will go beyond Metal Coatings and apply to all manufacturers challenged with testing energy-curable thin films. A webcast of the hearing can be found at https://www.youtube.com/watch?v=TG4APcoRmoE. Of interest are 2:14:08: Staff presentation; 2:19: Comments by Orange County Supervisor Janet Nguyen in support of RadTech’s requests; and 2:23: RadTech comments.
The district expects the metal coatings industry to fully implement the changes by December 5, 2034, with a price tag of approximately $3,000,000 to impacted businesses.
UV Curing Systems and Ozone
RadTech received an inquiry from an end user in Utah regarding the generation of ozone by mercury vapor UV curing systems. The geographical location causes trapping of pollution in a valley between the mountains – similar to the problem in Southern California. The end user wanted to be proactive with local regulators to address the issue of potential ozone emissions. RadTech’s Board of Directors’ Secretary Jennifer Heathcote took on the challenge of answering the question, “How much ozone is generated by mercury vapor UV curing systems?”
UV curing systems emit a combination of ultraviolet wavelengths classified as Vacuum UV (100-200 nm), UV-C (200-280 nm), UV-B (280-315 nm), UV-A (315-400 nm) and UV-V (400-450 nm). Vacuum UV and UV-C wavelengths shorter than 240 nm are capable of breaking the bonds of an oxygen molecule (O2) to produce two oxygen atoms (O and O). These oxygen atoms (O and O) combine with other oxygen molecules (O2) in the atmosphere to form ozone molecules (O3). As soon as this ozone (O3) is created, the molecular bonds immediately begin breaking apart to form an oxygen molecule (O2) and an oxygen atom (O). These single oxygen atoms (O) quickly combine to form oxygen (O2). The entire cycle happens relatively quickly.
The molecular bonds formed when the output from UV-curing lamps interacts with oxygen in the atmosphere to form ozone are not very strong. As the newly created ozone molecules are exhausted away from the curing system through closed ducting, they easily revert to oxygen. Because this happens quickly and with certainty, there is no accumulation of ozone over time. As a result, ozone generated by UV-curing systems poses no issue to the surrounding environment. It is best practice for UV-curing systems to be ducted away from the press or machine and outside the production facility roof. By the time the exhaust is emitted from the roof, it is basically warm air with negligible ozone. Exhausting to the roof provides a safe worker environment with no impact on the surrounding environment.
Government agencies regulate emissions that contain pollutants such as nitrogen oxides (NOx) and volatile organic compounds (VOCs). These pollutants react with oxygen in the presence of sunlight and high temperatures to form ground-level ozone, otherwise known as smog. High-temperature combustion processes generate these pollutants and are an indirect contributor to ground-level ozone formation, especially during hot, sunny weather. UV curing systems are all-electric processes and do not emit combustion contaminants such as NOx or VOCs. Therefore, they are not a direct cause of the ozone regulated by government agencies. Any direct ozone potentially generated by UV curing systems is unstable and has a very short life. The ozone generated by UV-curing systems does not contribute to smog.
It is difficult to calculate or predict the amount of ozone generated by UV-curing systems. It depends on system design, lamp power, lamp length, wavelength emission and airflow. Every installation is different. To know exactly, users can measure ozone concentrations at the press or machine, at the exhaust duct on the roof and at ground level outside the plant. Measured ozone concentrations will be negligible and well within safe exposure limits for properly designed UV-curing systems installed with sufficiently sized extraction fans and ducting.
On or about 2023, the South Coast Air Quality Management District conducted testing to measure ozone emissions from UV lamps used in air purifiers. Not only did the agency find that no ozone was generated, but one of the units actually removed ozone from the SCAQMD lab. According to the district, at all positions and fan speeds, the measured ozone concentration was 16-53% lower than the background laboratory ozone concentration. “This means the unit does not produce ozone and actually removes some ozone from the air,” read the report from the SCAQMD staff. The testing concluded that any ozone generation from the UV devices was well below the ozone limits mandated by the California Air Resources Board. Ultimately, the district included UV units in its air filtration program, which provides $13.7 million in grants for air filtration systems for public schools in Southern California’s most polluted areas.
Despite ozone from properly exhausted UV-curing systems being a non-issue, users still should consult local regulations prior to installation. Some communities require emissions permits anytime an exhaust hole is put in a roof. This requirement often is unavoidable despite the exhaust emissions having an inconsequential impact on the environment and the surrounding community.
Rita Loof
director of regional environmental affairs, RadTech International North America
rita@radtech.org
