Environmental Chemistry is a scientific discipline that uses the methods and results of chemistry to understand the environment. The discipline has arisen due to the recognition that chemical compounds, whether anthropogenic or natural, have important effects on naturally occurring processes and organisms. One of the goals of the discipline is to quantify these effects through controlled experiments and measurements.
Using the above mentioned approach, a fundamental understanding of the chemical processes occurring in a given system can be achieved. Some efforts in environmental chemistry aim to have a broader impact, for example by reducing the pollution that has been measured; in this context a fundamental chemical, physical and biological understanding of the dynamics of the system is necessary.
Pollution raises several questions
The identification of a chemical compound in the environment raises many questions. To give a few examples: Where does the compound come from? How was it produced and released? How is it transported within the ecosystem and what chemical mechanisms govern its removal? What effects does the compound have on the environment including organisms? How does the environment work, and what are the rules and ethics governing its use?
It is obvious that a rational treatment of these questions will involve results and methods from virtually all of the branches of science, supplemented by the humanities, social science, economics and the study of law. Environmental chemistry is thus a multidisciplinary subject, one in which a strong foundation in chemistry is paired with the broader perspective given by a number of related disciplines in order to provide insight concerning a broad range of problems.
Anthropogenic chemical pollution is not a new phenomenon
For example it is likely that lead was a widespread contaminant in ancient Rome, since it was used to line the aqueducts and to hold food and drinks. In the context of environmental chemistry it is important to emphasize that at that time there was no knowledge of the risks implicit in these uses. Environmental chemistry originated as a discipline when scientists began to investigate the connection between environmental problems and the occurrence of anthropogenic compounds in the environment. An important event in the development of the field was a severe episode of air pollution that occurred in London in December of 1952. The combustion of coal caused a thick smog (smog = smoke + fog) to cover the city; this event is blamed for an excess death of 4700.
Pesticides the reason for the “Silent spring”
The 1950s and 60s witnessed an accelerating use of chemical compounds in agriculture, industry and in the home, and at the same time more environmental problems were identified. In 1962 Rachel Carson published Silent Spring that described how the pesticide DDT is concentrated by the food chain, causing serious damage to the predators at the top of the pyramid. Silent Spring brought environmental issues to the attention to the public, and from that time, environmental issues have received broad coverage and support nationally and internationally. More recent examples include the Brundtland Report and the establishment of the Danish Ministry for the Environment and several sector research institutes.
In the 1970s it was shown that anthropogenic chlorofluorocarbons (CFCs) destroy ozone in the stratosphere. CFCs were discovered in the 1930s, and quickly found use as industrial solvents, refrigerants and foaming agents for manufacturing plastic and rubber. The fact that CFCs are non-toxic and inert contributed greatly to their success. However the inertness of these compounds turned out to be a problem since they are not removed by the atmosphere’s normal cleansing processes. The CFCs have atmospheric lifetimes that can be 100 years or longer, and they are removed largely by the slow process of transport to the stratosphere followed by photolysis. The key point is that the products of CFC photolysis destroy the stratospheric ozone layer that protects the biosphere from harmful UV radiation. The first treaty limiting the production of CFCs was signed in 1987, only 13 years after the groundbreaking discovery of their harmful environmental effects.
Awareness regarding the dangers of pollution has allowed environmental chemistry to grow into a discipline that concerns itself with the behavior of chemical compounds in water, soil, air, biological systems, and in many other media. It is therefore natural that environmental chemistry has advanced concerning complexity and detail, and today stands as a discipline where advanced chemical analysis and computer models are among the most important tools.
Focus points of an environmental chemist
An increased understanding of the environment has meant that the focus today is not only on the chemical compounds that have an immediate poisonous effect on the environment. There is also an interest in compounds that can bioaccumulate and biomagnify (for example in Arctic environments) and in groups of compounds that can have a combined effect. These compounds may be involved in individual steps of a chain of reactions that results in unwanted effects that may only first appear long after the initial exposure. One important result has been the recognition that a series of compounds can affect hormone systems. These compounds are believed to be responsible for deformations of the sexual organs of certain animals (e.g. fish, snails, frogs and alligators). These compounds may also be involved in the reduction of the quality of male’s sperm that has been seen in many western countries. In this context, attention has been directed towards new compounds that have not before been the subject of environmental chemist’s interest. For example, recently both medicines and naturally occurring plant toxins have been the subjects of research in environmental chemistry.