130 SUSTAINABILITY
Biodegradation testing There are clear test methodologies used to determine biodegradation and the rating system is also clearly defined. The OECD in their guidelines (1981b, 1991, 1992a, 1992b, 2001, 2002, 2004a, 2008) distinguishes six forms of biodegradation (Table 2).8 Looking at Table 2, there are three important
factors that are needed to successfully navigate biodegradation test analyses. Diversity of tests - a number of tests that can
be utilized and selection is the key. Specifying the test used to be evaluated. Specifying the percentage of the actives
being tested. There is also some misunderstanding about the nature of the tests that best define biodegradation. A potential problem with biodegradability values is deciding if biodegradation should be run on a single raw material or on the finished formulation. Since solubilization of biodegradable oils
present in a formulation can dilute materials being tested, they can also solubilize oils. Put simply, the finished formulation appears to be the most important when choosing what to evaluate since it is in fact what gets into the environment.
2. Renewable Renewable is defined by the OECE as something capable of being maintained at a steady level without exhausting natural resources or causing severe ecological damage.
TABLE 2: OECD DEFINITIONS OF BIOGRADATION
1. Ultimate biodegradation (mineralization): The level of degradation achieved when the test compound is totally utilized by micro-organisms in the production of carbon dioxide, water, mineral salts and new microbial cellular constituents (biomass).
2. Primary biodegradation (biotransformation): The alteration in the chemical structure of a substance, brought about by biological action, resulting in the loss of a specific property of that substance.
3. Readily biodegradable: An arbitrary classification of chemicals which have passed certain specified screening tests for ultimate biodegradability; these tests are so stringent that it is assumed that such compounds will rapidly and completely biodegrade in aquatic environments under aerobic conditions.
4. Inherent biodegradable: A classification of chemicals for which there is unequivocal evidence of biodegradation (primary or ultimate) in any test of biodegradability.
5. Half-life (t0.5): The time taken for 50% transformation of a test substance when the transformation can be described by first-order kinetics; it is independent of the initial concentration.
6. Disappearance time 50 (DT50): The time within which the initial concentration of the test substance is reduced by 50%.
Of particular relevance to the personal care industry is the OECD’s statement that “sustainable chemistry is a scientific concept that seeks to improve the efficiency with which natural resources are used to meet human needs for chemical products and services.
Sustainable chemistry encompasses the design, manufacture and use of efficient, effective, safe and more environmentally benign chemical products and processes.”9 The OECD adds: “Sustainable chemistry is also a process that stimulates innovation
PERSONAL CARE April 2023
www.personalcaremagazine.com
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