Chlorine: the only green element – towards awider acceptance of its role in natural cycles

Approximately 2000 compounds of chlorine, both inorganic and organic, are known to be produced, transformed, transported and degraded in a range of natural geological, chemical or biochemical processes in most of the earth’s environmental compartments. Chloroform, chlorophenols, chloroacetic acids and polychlorinated dibenzo-p-dioxins and dibenzofurans, long believed only to have arisen from man’s activities, have significant natural sources, some of which predate industrialization. The presumption that such materials are solely man-made must now be seen as incorrect. In fact, sufficient is known to suggest that natural cycles involving both organic and inorganic chlorine should be more widely recognised. Their characteristics should be more fully understood so as to put emissions of related synthetic materials and associated control and remediation measures into better context. The role played by organochlorine compounds, synthesised and utilized by a range of aquatic and terrestrial organisms (including humans) and the biosynthetic pathways leading to their formation and transformation are areas of research worthy of further study.