Environmental Problems, Their Causes, and Sustainability 1

How Dangerous Are Dioxins? ControversyOver Unintended CulpritsDioxins are potentially harmful chlorinatedhydrocarbons produced as by-products of variousindustrial processes such as waste incineration andpaper bleaching.Dioxins (or polychlorinated dibenzodioxins) are afamily of more than 75 different chlorinated hydrocarboncompounds. They form as by-products in hightemperaturechemical reactions involving chlorineand hydrocarbons.Dioxins (or polychlorinated dibenzodioxins) aremainly unwanted by-products or unintended consequencesof a wide range of industrial processes. Naturalprocesses such as forest fires and volcanic eruptionsalso produce them.Worldwide, incineration of municipal and medicalwastes accounts for about 70% of dioxin and furan releasesto the atmosphere. Other sources include woodburningfireplaces, coal-fired power plants, metalsmelting and refining facilities, wood-pulp and papermills, and sludge from municipal wastewater treatmentplants.Toxicology studies indicate that about 30 dioxincompounds have significant toxicity. One dioxin compound,TCDD, is the most toxic (Table 19-1, p. 414) andthe most widely studied. Dioxins are persistent chemicalsthat linger in the environment for decades, especiallyin soil and human fat tissue. About 90% of thehuman exposure to trace levels of dioxins occursthrough eating contaminated food.There is concern about possible harmful healtheffects on humans and wildlife from exposure to lowlevels of dioxins. A 2001 draft report of an EPAsponsoredcomprehensive review of the scientific literatureby more than 100 scientists around the worldcame to three major conclusions.First, TCDD is a human carcinogen, and otherdioxin compounds are likely human carcinogens, especiallyfor people who eat large amounts of fattymeats and dairy products. Second, the most powerfulpossible effects of exposure to low levels of dioxin onhumans are disruption of the reproductive, endocrine,and immune systems (Case Study, p. 416) and harmfuleffects on developing fetuses. Third, very low levels ofdioxin in the environment can cause serious damageto certain wildlife species. But industries producingdioxins say the dangers of long-term exposure of humansto low levels of dioxins are overestimated.Because it will take decades to resolve these issues,some environmental and health scientists call for usinga precautionary strategy to sharply reduce emissions ofdioxins now. This would be done mostly by banningthe use of chlorine for bleaching paper (as severalEuropean countries have done) and eliminating chlorinatedhydrocarbon compounds that produce dioxinsfrom hazardous wastes burned in incinerators, iron oresintering plants, and cement kilns.A 2003 report by the National Academy of Sciencesrecommended that the United States take precautionarysteps to reduce dioxin levels, especially in food. Thepanel of medical experts called for testing livestock forageand feed for dioxins, setting lower limits for dioxinsin food products and dietary supplements, and testingthe products for dioxin levels. They also said thegovernment should encourage people to eat less fatand meat, which tend to have higher levels of dioxins.Bad news. These things are not being done.24-9 HAZARDOUS WASTEREGULATION IN THE UNITEDSTATESWhat Is the Resource Conservation andRecovery Act? Tracking Hazardous Wastefrom Cradle to GraveU.S. firms producing fairly large amounts ofhazardous waste must get a permit from the EPAand submit a record tracking these wastes fromproduction to disposal.In 1976, the U.S. Congress passed the Resource Conservationand Recovery Act (RCRA, mentioned previously)and amended it in 1984. This law has three major requirements.First, the EPA is to identify hazardouswastes and set standards for their management bystates. Second, firms that store, treat, or dispose of morethan 100 kilograms (220 pounds) of hazardous wastesper month must have a permit stating how suchwastes are to be managed. Third, permit holders mustuse a cradle-to-grave system to keep track of waste theytransfer from a point of generation (cradle) to an approvedoff-site disposal facility (grave) and submitproof of this to the EPA.What Is the Superfund Act? Cleaning UpAbandoned Waste SitesIn the United States, the EPA identifies abandonedhazardous waste sites, cleans them up, and sends thebill to all responsible parties it can find.In 1980, the U.S. Congress passed the ComprehensiveEnvironmental Response, Compensation, and Liability Act,commonly known as the CERCLA or Superfund program.Through taxes on chemical raw materials, thislaw plus later amendments has provided a trust fundto achieve three goals.One is to identify abandoned hazardous wastedump sites (Spotlight, p. 559), underground tanksleaking toxic chemicals, and other hazardous wastesites. Second is to protect and if necessary clean upgroundwater near such sites and to clean up the sites.558 CHAPTER 24 Solid and Hazardous Waste