Estimating Chemical Properties
Environmental scientists try to find out where a chemical goes in the environment and what it does when it gets there. Do bacteria and other microorganisms break the molecule down to nutrients and other naturally occurring chemicals (biodegradation)? Does this happen quickly or slowly? Does the molecule evaporate? Does the molecule break down in the atmosphere (photolysis or photodegradation)? Does the chemical stick to the soil and sediment particles or stay in the water column (sorption) or stay in the water column? Will the compound be toxic? While there are a lot of different laboratory methods used to answer each of these questions, the first step is often to use a Quantitative Structure Property Relationship (QSPR).
Every molecule has many different chemical properties. These properties include things like solubility in water, volatility (how quickly the molecule evaporates), the boiling and melting point and the solubility of the molecule in fat. Each of these properties tells the scientists something about how the chemical will act in the environment or in an animal. QSPRs help scientists understand whether a compound is likely to bioconcentrate in fish, biodegrade and be converted to CO2, etc. From any one property, it is difficult to fully understand what will happen to a chemical in the environment. To get a full understanding of where an ingredient goes in the environment, many chemical properties are used with environmental fate models. If environmental behavior can be predicted with equations, the process of risk assessment can be greatly sped up.
In some cases, QSPRs alone do not provide sufficient data to accurately estimate environmental concentrations. When this occurs, environmental fate testing is conducted.