For example, if DCHA was an exceptional corrosion inhibitor, emulsion stabiliser, or buffer, its use might be justifiable. Truly biostable additives should have benign toxicity profiles and when tested in MWF formulations, they should generate data similar Figure 1a. The use of less toxic, biostable MWF formulation components reflects best practice.
the use of pictograms their customers might find alarming. However, this approach is paradoxical. Biocide labels include much more health and safety information than technical grade products do. Many industry stakeholders believe that less information means less risk. Uneducated customers tend to assume that biocidal products are inherently more toxic and less safe to handle than technical grade products. The same end users that use concentrated acids (hydrochloric acid’s acute oral, dermal, toxicity LD50s
are 236 mg kg-1 kg-1 to 277 mg kg-1 , >5010 mg , respectively and its inhalation toxicity is 1.66
mg L-1) routinely, are reluctant to use biocides. This reflects the reality that outrage – emotional rather than fact-based resistance – typically overrides rational evaluation of data. The equation used to define risk is:
Hazard = Risk x Exposure.
Figure 2: Acute oral, inhalation, and dermal toxicities of the registered biocide, Hexahydro-1,3,5-tris(2-hydroxyethyl)-s-triazine (HHT) and Dicyclohexylamine (DCHA) – an amine commonly used as an alternative to biocides in metalworking fluid formulations.
Why do compounders use unregistered biocides? The toxicity data needed to support BPR dossiers is typically at least 10x as expensive to develop as the data set needed to support technical product registration under ECHA. Consequently, biocides are considerably more expensive than other MWF functional additives. Compounders are under continuous pressure to reduce product costs. End-user purchasing agents tend to focus on cost per unit rather than annualised costs. Moreover, compounders commonly attempt to minimise the need to add Global Harmonised System pictograms – particularly the skull and crossbones and exploding chest pictograms. During the early years of REACH’s conceptual development, there was some indication that all chemicals sold in the EU would have comparable toxicology and environmental fate data. That would have leveled the playing field between biocidal products and technical chemicals. The economics of making the data requirements for all chemicals similar to those for biocides was deemed unaffordable and impractical. Consequently, BPR dossier data requirements remained substantially greater than those for non-BPR registrations.
In addition to the cost issue, avoiding the use of registered biocides, compounds may be able to avoid
Regardless of the hazard (determined from toxicity data), risk decreases as exposure decreases. For example, high voltage powerlines represent a high health hazard, but only if you touch them. Education is the answer to outraged-based product selection decisions.
Conclusions In recent years the number of different active substances available to treat MWF has shrunk from more than 200 to fewer than 30. Biocide manufacturers are opting to withdraw products that are not also approved for use in high volume applications (e.g., oilfields, paints and coatings, and household, institutional, and industrial products). Although biostable MWF can sustain bioburdens that would degrade non-biostable MWF, high bioburdens in MWF increase the risk of allergenic disease and the release of malodorous gases. At present, some of the chemical products being used to replace biocides are more toxic than registered biocidal products. No biocidal substance is universally effective in all MWF. Therefore, there is a risk that microbial contamination control will be increasingly challenging if the number of options continues to decrease. For the foreseeable future, effective MWF biocides will remain important functional additives.
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LUBE MAGAZINE NO.181 JUNE 2024
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