POPULATION, WASTE AND CHEMICALS
umans have found chemicals essential for modifying and controlling their environment from the earliest times. Ancient civilizations smelted metals for tools, weapons and ornaments and these operations produced chemical wastes. The Romans conducted metal mining and smelting operations in many parts of their empire and the resulting environmental impacts are still measurable today; lead levels in some soils in several parts of England still reflect metal processing carried out 2 000 years ago .
The industrial revolution saw a massive rise in population accompanied by an increase in industries of all kinds. Textiles, steel, glass and soap manufacture were all dependent on the ready availability of basic chemicals like sulfuric acid and the alkali sodium carbonate. The chemical industry was born as the technology to mass produce these commodities developed.
Our current standard of living would be impossible without industries such as steel, non-ferrous metals, power generation and chemicals manufacture. However, they have also had a profound effect on our environment. Our bodies and our surroundings are contaminated by their wastes. Soil, atmosphere and water contain reservoirs of waste metals and organic chemicals which reach us through our food, drinking water and the air we breathe. [Add]
One chemical that has had a particularly strong environmental impact is chlorine. Chlorine was originally a waste product of alkali manufacture, but as the 20th century progressed it found many new uses. The chlorine industry grew rapidly following the Second World War, producing products such as pesticides, solvents, dry cleaning fluids and PVC plastic. These goods brought many advantages, and it was not until the 1960s and 1970s that it was recognized that many chlorine compounds were toxic and environmentally persistent.
Polychlorinated biphenyls (PCBs) are an example of the early products of the chlorine industry which were to prove highly damaging to the environment. PCBs are non-flammable oily liquids or waxes which found uses as hydraulic fluids, as additives to oils, in sealants, in electrical applications and in paints. First manufactured in 1929 in the United States, evidence that they were persistent, accumulated in plants and animals, and toxic became overwhelming in the 1960s. Because of the large number of different PCBs it has proved difficult to untangle all of their toxic impacts, but many are suspected of promoting cancers, damaging the immune and reproductive systems and interfering with hormone systems through endocrine disruption. Particularly disturbing is evidence that children born to mothers contaminated with high levels of PCBs suffer impaired nervous system development . The products were phased-out or banned in Western countries in the 1970s, though their manufacture continued in Eastern countries for many years more. [Add]
Not all chemical pollutants are deliberately manufactured. The by-products and compounds of chemical processes can be transformed in the environment into different, sometimes more hazardous, breakdown products. Dioxins, for example, are by-products of combustion and waste incineration processes. The rapid increase in the use of coal as a fuel during the 19th century increased dioxin pollution. But a second factor which resulted in a steep increase in their generation was the chlorine industry. Dioxins are generated by many chemical processes involving chlorine and are found in wastes from PVC manufacture, and as contaminants in chlorine-containing products including some pesticides and dyes . [Add]
Safe disposal of hazardous waste products like PCBs presents a problem. PCBs in landfills may vaporize and turn up in landfill gas or escape to the air. The safest disposal method is by incineration in a purpose-built hazardous waste incinerator. However, even this method has drawbacks. Poorly designed or badly operated incinerators may spread PCBs or other contaminants rather than destroy them. In 1993, an incinerator at Pontypool in Wales was found to have been polluting local soils and food with high levels of PCBs and dioxins .
Past disposal of hazardous waste has often been the cause of environmental problems. The dumping of waste at sea was once a widespread practice. It was difficult to regulate and its effects on the marine environment impossible to monitor. However, international agreements made under the 1972 London Convention have gradually succeeded in reducing the number of countries dumping at sea. Many European nations have not only agreed to stop the sea disposal of industrial waste, but also the dumping of sewage sludge -- contaminated with toxic metals and dioxins -- and radioactive wastes.
Hazardous wastes have also been exported to developing countries which have no facilities to dispose of them, and whose people have little knowledge of the hazards they represent. Efforts to control the trade in hazardous waste began in 1989 with the Basel Convention. A blanket ban on the export of hazardous wastes from developed to developing nations has been agreed and is now applied -- although it still awaits formal legal completion. [Add]
In developed countries there is increasing control of industrial waste and its disposal. There is good evidence, for example, that emissions of PCBs and dioxins are declining, and so too is human exposure . But there is a clear need for the international community to ensure that developing countries are able to impose sufficient controls on their industries to minimize the generation of hazardous wastes and ensure their correct disposal in order to protect the health of their populations and the global environment. [Add]
Many lessons have been learned from the experience of the last 50 years. However, there are an estimated 100 000 chemicals on the market and their ecotoxicity and biodegradability are often poorly studied . Although international rules now require testing of the new chemicals produced in large volumes, there is an enormous backlog of compounds for which full hazard and toxicity data have never been produced. Modern chemical analytical techniques show that sewage sludges and waters receiving industrial and domestic effluents contain cocktails of thousands of chemicals -- waste products, by-products and breakdown products of modern chemical goods from fragrances to flame retardants.
Attempts to assess the risks -- and to introduce new controls on their use -- have proved to be a lengthy and contentious process. Risk assessments are imperfect because they cannot take into account all the possible interactive effects between different compounds . It is also not yet possible to assess the safety of endocrine disrupting chemicals because their effects are not sufficiently understood and test methods still have to be commonly established. [Add]
The presence of so many pollutants in the environment begs the question of whether society should adopt a more precautionary approach to the release of chemical wastes. New ideas for regulating chemicals include strategies which give the environment the benefit of the doubt when data on toxicity and environmental fate are lacking. For example, an agreement reached by many countries surrounding the North Sea, under the OSPAR treaty in 1998, aims to reduce levels of manufactured chemicals in the environment by "continuously reducing discharges" of hazardous substances with the aim of achieving environmental concentrations "close to zero" for all synthetic substances by 2010 . [Add]