Persistence: Defining How Substances Break Down
Persistence is the propensity of a substance to remain unchanged in the environmnet and this is a major focus of regulations for the registering of substances. Persistence is determined by quantifying the rate of degradation in different environmental matrices.
In order to help define the our environmental footprint, we are expected to have a state-of-the-art understanding of the environmental fate of its medicines, their human metabolites and those chemicals used in manufacturing (collectively termed "substances"). This drives the Predicted Environmental Concentration (PEC) fundamental to risk assessment. The following projects are examples of current work in this area.
- Environmentally realistic biodegradation of chemical substances. Most substances will reach the environment via municipal Sewage Treatment Plants (STPs). This project has shown that accurate prediction of substance removal often requires the use of STP simulation methods, working at environmentally relevant levels of the chemical substance, rather than traditional batch methods.
- Marine biodegradation testing. Globally, many people live near coastal zones and substances may enter the marine ecosystem via STP effluents. This project is addressing the pattern of substance breakdown by marine microbes.
- Terrestrial fate studies. In some cases, sludge produced by domestic or industrial STPs may contain residues of many substances. This work is now looking at how chemicals breakdown in soils and also how soil microbial processes (important in maintaining soil fertility) may be impacted by substances. Some of this work is being conducted in cooperation with several EU partners.
- Photo-transformation science. Given evidence that some substances are broken down in sunlight, AstraZeneca has recently initiated work into understanding how pharmaceuticals and structurally related substances can be broken down by photochemical methods.
