Chlorine Quandary

By Jim Wilson

If civilization has a smell, it is the cleansing scent of chlorine bleach. It’s barely detectable aroma announces the water is safe, the surroundings are sanitary. Before the introduction of chlorinated tap water, cholera and typhoid were as common as the office cold. The protective power of chlorine resides in its reactivity. It is a bully of a chemical that punches through the cell walls of bacteria and shatters viruses. And chlorine’s muscle comes cheap. Most of the Earth’s surface is covered with salt water. Zap it with electric current and the sodium and chlorine atoms go their separate ways. use the chlorine to disinfect a water supply or to deliver it. Chlorine is also a prime ingredient in making plastic pipes. Drinking water is just the start. Chlorine based pesticides civilized the tropics by eradication disease carrying mosquitoes and timber-chopping termites. Chlorine based refrigerants put safe refrigerators in our kitchens and air conditioning in our cars. You would be hard pressed to find any industry that could exist without at least one chlorine containing chemical. And it is precisely because of this popularity that a growing number of environmental scientists and public health experts agree that chlorine should be banned.

It is slowly becoming clear that chlorine is a chemical whose time has passed. Persistent organic pollutants (POP’s) threaten the health and well being of humans and wildlife in every region of the world, says John Buccini, a Canadian government representative to the United Nations Environmental Program (UNEP). After seemingly endless scientific debate, the United Nations arrived at a list of the 12 most globally threatening POP’s. It came as a surprise to no one who follows environmental had health issues that each is a chlorine bearing compound, a member of a group of chemicals known as organochlorines.

In study after study, exposure to these chemicals has been demonstrated to increase the risk of cancer and birth defects. They provoke allergic reactions and damage the nervous, reproductive and immune systems. Some organochlorines mimic the hormone estrogen, thus altering wildlife in ways that diminish their ability and interest in producing offspring. Organochlorines are also some of the enduring compounds. Once introduced into the environment, it can take years, even decades for POP’s to break down to less damaging forms. And if all this were not reason enough to be cautious, POP’s have one final fatal flaw- an affinity for fat. Our fatty tissue soaks up POPs like a sponge takes in water. The technical term is bioconcentration. UNEP scientists say that in some animals POPs have been detected at levels 70,000 times higher than in their surroundings.

A Global Ban

In December, diplomats from 122 countries met in Johannesburg, South Africa, to take action. In a series of earlier technical meetings, POPs had, in effect, been tried and convicted. The international consensus was that nature had endured enough damage. “This new treaty will protect present and future generations from the cancers, birth defects and other tragedies caused by POPs,” says Buccini, who chaired the session. The treaty marked a dozen organochlorines for banishment. Eight are pesticides. DDT is the most recognizable name. If you are a farmer or serious gardener, or worry about termites eating your home’, you will recognize the others: aldrin, chlordane, dieldrin, endrin, heptachlor, mirex and toxaphene. Two of the POPs are industrial chemicals. although one group, PCBs, is a household word in many parts of the United States. For decades. residential streets of America wire lined with utility poles atop which sat transformers insulated with PCB fluids. PCBs were used as paint additives and plastics. Unless your work involves manufacturing fireworks. ammunition or synthetic rubber, you probably were not aware that the pesticide hexachlorobenzene is also a highly dangerous industrial compound. This doesn’t mean that you weren’t exposed. At one time, the compound circulated widely in the atmospheric, a byproduct of manufacturing carbon tetrachloride and similar Cleaning compounds.

Two unintentionally manufactured families of compounds, dioxins and furans, complete the list. Collecting of some 210 separate but similar compounds, they are released in the making of pesticides, polyvinyl chloride and chlorinated solvents. Before the synthetic chemical industry blossomed in the 1940 ” these compounds were chiefly released when waste, coal, peat or wood was burned.

The treaty will ban most POP’s immediately. Environmentalists are hopeful it will usher in a new era, a sort of chlorine sunset in which organochlorines are replaced by more environmentally benign agents. Ozone, a molecule made of three, rather than two, oxygen atoms and for this reason highly reactive, can replace chlorination in many applications, including drinking and swimming pool water disinfection and bleaching. The downside is that it is expensive technology. And, unlike chlorine, ozone quickly dissipates.

In several applications, organochlorines are not so easily re- placed. Chiefly for this reason, the chlorine industry championed all won health-related exceptions for DDT, to control malarial mosquitoes. A similar go-slow approach will be taken with PCBs. Governments will have until 2025 to order companies to arrange for PCB-free replacements. Neither the environmental group Greenpeace, which wants a virtually total prohibition on chlorine chemistry, nor the Chlorine Chemistry Council, an industry group, which sees the United Nations’ brush as painting too broadly, is entirely happy with the treaty.

But Klaus Topfer, UNEP’s executive director, defends the group’s work. “This is a sound and effective treaty that can be updated and expanded over the coming decades to maintain the best possible protection against POPs,” he says. For one thing, the treaty will be liberally sprinkled with special exemptions. Despite UNEP’s sweeping promises, the final wording of the treaty will contain more than 100 country-specific exemptions. most to allow longer phase-out times.

But everyone agrees the treaty is a start. The United Nations will formally sign the treaty at a diplomatic conference in Stockholm in late May of this year. This might seem like the end of a long road for a treaty that was initially proposed in 1995. but in an important sense it is only the beginning. Before the POPs ban can take effect, it must be ratified by 50 of the governments that participated in the talks last December. If the United Nations’ experiences with similar efforts are a guide. it could be several years be- fore the treaty takes effect.