In terrestrial plants, organochlorines often act as anti-feedants to protect the plant from attack by insects or herbivores. However, it is not justifiable to claim that they are primarily the result of man-made chlorine processes. An Ecuadorian tree frog produces a natural organochlorine pain-killer many times stronger than morphine Forest fires, volcanic eruptions and even compost heaps are all sources of dioxin in the environment. In recent years, scientists have found that many chlorinated and halogenated compounds have been formed naturally in the environment long before chlorine was discovered. For example, dioxins have been found by Japanese scientists in sediment up to 8,000 years old.
Chlorine is naturally present as organic compounds in the sea, in rivers and in plants.
The natural production of organic chlorine compounds actually exceeds that of industry, and is essential to many forms of health protection. It is important to identify how nature recycles chlorine and uses it to create new compounds, so that industry can learn from nature and implement this in its production processes. Chlorine and its compounds are natural components of the Earth - as every element has its place in biosynthesis, so it is with chlorine too. Almost 5 million tonnes of methyl chloride, 0.3 million tonnes of methyl bromide and 1.3 million tonnes of methyl iodide which occur naturally in the sea each year, as well as large tonnages of various other poly-halogenated methane derivatives, including chloroform and carbon tetrachloride, far exceed the industrially manufactured amounts of these chemicals. In addition, chlorine is brought in by oceanic aerosols, volcanoes and weathering.