Key Ingredients for a Biocide Manifesto
February 3, 2021
A biocide manifesto for the paint and coatings industry would essentially state that antimicrobial control is critical for product performance, brand reputation, sound regulatory alignment and socio-economic growth. The only way this can be achieved is with collaborative, evidenced-based decision making between industry and government on both sides of the Canada-United States border. Refusal to approve registrations for certain biocides, or decisions to hastily impose additional label rate restrictions has a long-term, negative affect on the number of highly performing, eco-friendly paint products that can be imported, manufactured and sold in Canada.
The Canadian paint industry continues to face complicated trade-offs between the ‘formulation-driven’ trend toward higher preservative concentration levels needed in waterborne coatings due to recent VOC regulations, versus the ‘regulatory-driven trend’ toward lowering paint preservative concentrations generally. It is a trend that will lead to unsafe thresholds for biocides used in coatings formulations leading to increased bans, restrictions and/or increased hazard communications related to risks of residential and occupational safety incidents.
A more focused and integrated approach is needed to reconcile these two divergent trends. This must be addressed on both sides of the border in biocide re-evaluations and related risk calculations. For example, dermal absorption values cannot be made without considering the dose of a substance that actually reaches systemic circulation following dermal uptake. Similarly, systemic absorption (bioavailability) after inhalation exposure cannot be determined without consideration of differences in regional disposition within the respiratory tract as a function of particle size. Failure to factor into the risk calculation the dose available for systemic exposure, while utilizing toxicological endpoints, distant from the site of exposure, increases the likelihood of unrealistically high exposure estimates, which then produce unusually high-risk calculations. That in turn will, unnecessarily, lead to more bans and use restrictions for biocides.
CPCA stresses the importance of a more efficient and better aligned North American review process for biocides to maintain fair trade in products and easy access to a sufficient number of biocides in both countries for paint manufacturing. This recognizes the relevance of a highly integrated Canada-US economy and new efforts for increased cooperation under the recently signed free trade agreement, the USMCA. Over the past several months large North American manufacturers also considered the evaluation of several active paint biocides assessed by the US-EPA. These included sodium pyrithione, ITAs (Isothiazolinones), carbendazim, folpet and DBNPA (Dinitrobenzonitrile propionic acid). Under the recent PMRA ‘paint cluster analysis’ Canada addressed only two of the biocides in common with the recent US-EPA publications: sodium pyritione (or sodium omadine) and folpet. Although this common approach may be purely coincidental, CPCA views this as a very positive sign as both agencies will further synchronize re-evaluation processes and harmonize the timelines going forward.
The concurrent assessment of several paint-related biocides in Canada and the United States in 2020 raised a number of serious industry concerns. First and foremost, it limits industry’s ability to maintain the current, and already limited, array of biocides in both countries for paint preservation for dry film and in-can applications. Industry must have access to those biocides to sustain existing performance levels during paint manufacturing, transportation and storage, for all types of Architectural and Industrial paint formulations. CPCA believes that the US-EPA and the PMRA should consider life-cycle assessment (LCA) for all paint preservatives available in future evaluations and re-evaluations.
The value of the LCA would not necessarily be on the biocide itself, but as it relates specifically to the function and role within a product system or formulation. By doing so, the LCA could capture the benefits that preservatives provide in the system versus just focusing on their footprint. It is an important overall consideration with respect to product stewardship generally. A lifecycle assessment would capture the environmental performance of various architectural coating preservative scenarios used to determine the environmental impacts and benefits that wet-state and dry-film preservatives provide in architectural coating systems. It would also provide necessary insight on how reducing, eliminating, or replacing certain preservatives can impact the coatings’ overall sustainability profile. It can also reveal how substitutions can alter the efficacy of those products and thereby increase product losses, environmental wastes and, indeed, health issues.
While preservatives have been reported to cause both local and systemic effects, the use of these assumptions for risk calculations associated with systemic endpoints will require further consideration of the mechanics that govern substance transfer from the site of exposure to systemic circulation. This is especially critical in light of the fact that PMRA recently used critical systemic toxicological endpoints that were remote from the site of exposure such as thyroid effects, reproductive and developmental toxicity, rather than ‘local’ toxicological endpoints in selecting points-of departure (PODs) for risk calculations. This is a critical deviation from standard practice for biocide evaluation and overstates the risks by a significant margin.
Evaluation of biocides must accept the fact that: 1) exposure via dermal contact is a two-step process involving dermal uptake and transfer into systemic circulation; and 2) that systemic transfer following dermal uptake is in fact minimal. The dermal exposure values often assumed by Regulatory Authorities in their risk re-evaluation account only for dermal uptake, but not the transfer into systemic circulation, considering when a system (not a local toxicological endpoint) is used to determine the point of departure (POD) for risk calculations. As such, it renders dermal adsorption values unnecessarily high. Hence, the extent of dermal exposure that is utilized in re-evaluations is then considered much to conservative and which would not be encountered in the real-world application of paint products containing the biocides being evaluated.
Some biocide chemistries may negatively impact critical paint properties including – but not limited to – color, tint strength, gloss, scrub and stain resistance. Paint manufacturers are therefore reluctant to alter their preservative packages. The sophistication and uniqueness of paint and coatings formulations makes it difficult to select a preservative. The selection of a biocide is governed by a variety of factors, and it must be understood that “one biocide does not fit all” formulations. Use of an alternative, of a similar chemistry or very different chemistry, requires a significant investment of resources, both financial and personnel, to test a variety of paint properties that could be impacted by further restrictions. Of greater concern is the dry film preservative because replacement of a dry film biocide requires a minimum of three to five years of exterior exposure on a test fence or substrate in the region(s) in which the paint product will be sold.
Regulatory Authorities must also ‘integrate’ socio-economic studies into the re-evaluation process for biocides. Regulatory Authorities cannot continue to systematically ignore the negative economic impact of their evaluations, especially in the context of a very limited number of preservatives remaining in Canada for paint formulators. Rather than further reducing current use rates and banning more preservatives through individual assessments, risk assessors must carefully examine health effects along with economic effects, possible alternatives, availability and function of biocides, etc. Then, jointly with industry, then consider all options available for certain problematic types of formulations and related risks. This is typically done in the United States late in the evaluation process, and after the risk evaluation is completed. It can also be done concurrently with the risk evaluation. CPCA suggests a process be established to address such matters outside the formal re-evaluation process, which can be incorporated, when and as needed, for specific biocides. This is critical for alignment in a highly integrated value chain.
Canadian paint formulators should also be able to use non-PMRA registered biocides in paint mixtures that are destined for exports to countries where they have been risk assessed and are considered safe to use. The very rigid position currently taken by the PMRA is incomprehensible. It means that Canadian paint formulators cannot use certain biocides to treat paint articles for ‘export only’ to the United States and throughout the world. This is another socio-economic aspect that must be examined closely in any future decision in Canada.