Environmental Concerns

The use and disposal of chromium and chromium compounds have received much regulatory attention because of the toxicity of chromium and indications that it is a cancer-causing agent. A summary of studies on the mutational effects of chromium compounds in bacteria, mammalian cells, and human cultures was published in 1986 (Ref 20). In 1993, a listing of hazardous chemicals stated that "Chromate salts are suspected human carcinogens producing tumors of the lungs, nasal cavity and paranasal sinus" (Ref 21). This list indicates that some type of mutational data was reported for all chromium compounds. Hexavalent chromium compounds appear to be the most severe; most are designated as "confirmed carcinogens." One trivalent chromium salt, Cr(III) acetate, is now also a confirmed carcinogen. Other Cr(III) salts are classified as "questionable human carcinogens."

To quote an earlier researcher in this field, "One of the biggest needs involving the future use of conversion coatings [for aluminum] in aerospace is to find non-toxic substitutes for those chemical processing solutions which are now labeled as pollutants" (Ref 3). Only aerospace was mentioned, because restrictions were expected to be first observed with aluminum fabricators due to the role played by the federal government in setting standards for aircraft manufacture. In the years that have elapsed since this statement was made, very few chromium-base treatments have been replaced by environmentally safer technology, and restrictions continue to be imposed on the levels of chromium in waste water effluent, solid waste, and the air to which workers are exposed.

In the United States, regulations regarding hazardous waste disposal and monitoring proliferated from the mid-1970s through the 1980s. Congress passed several laws empowering the Environmental Protection Agency (EPA) to set regulations for the control of hazardous waste (see Ref 22 for a review up to 1991). Much of this legislation espouses "cradle-to-grave " management of hazardous waste. Some of the principal legislation enacted by Congress includes the Resource Conservation and Recovery Act (RCRA) of 1976, the Safe Drinking Water Act (SDWA) of 1974, the Toxic Substances Control Act (TSCA) of 1976, the Hazardous and Solid Waste Act Amendments (HSWA) of 1984, and the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA or Superfund) of 1980. Most of these laws have been amended (i.e., reauthorized) at least once since their initial passage. In a number of cases, considerable time passed after enactment of the law before the EPA was able to put the basic regulatory framework together (e.g., 4 years elapsed after passage of RCRA before the basic regulatory structure was in place). HSWA resulted from Congress's dissatisfaction with the EPA's progress with RCRA. All regulations are first published in the Federal Register, after which they become part of the Code of Federal Regulations under Title 40, which deals with protection of the environment.

As a result of these laws, chromium and its compounds became specific targets for regulatory control. In 1975 the National Institute for Occupational Safety and Health (NIOSH) recommended a standard for occupational exposure to Cr(VI) (Ref 23). The document described a number of studies that detailed medical problems observed by workers exposed to chromium. Included in this report was evidence indicating that certain Cr(VI) compounds were carcinogenic. The List of Suspect Carcinogens published by NIOSH now contains a number of chromium-containing compounds.

As a result of regulations enforcing RCRA, all facilities involved in electroplating were forced to comply by 1 July 1984 with the Electroplating Pretreatment Standards that appeared in the 28 January 1981 Federal Register (Ref 24, 25, 26, 27, 28). These standards were later broadened to include the anodizing and conversion coating industries; they were also made more stringent in the Metal Finishing Regulations that were printed in the 15 July 1983 Federal Register and enacted in 1986 (Ref 24, 25, 26, 29). Both sets of regulations were imposed by the EPA through local publicly owned treatment works. These regulations placed discharge limitations on various metals, such as chromium, and on other substances, such as those containing cyanide. Total chromium was limited to 2.77 mg/L/day, with a monthly average of 1.71 mg/L/day, and total cyanide was limited to 1.20 mg/L/day, with a monthly average of 0.65 mg/L/day.

In 1986, chromium and its compounds were put on the Community Right-to-Know List, which resulted from the Superfund Amendments and Reauthorization Act (SARA) of 1986 (Ref 21, 22). SARA established the Community Right-

to-Know Program, which requires industry to provide information on the type of chemicals being used at their facility. This was only the beginning; many other regulations governing chromium compounds have been promulgated.

As of the time of this writing, the 1994 session of Congress is expected to pass a second reauthorization of the Clean Water Act (enacted in 1972 and first reauthorized in 1986) that will reflect the "polluter pays" philosophy (Ref 30). The intent of this reauthorization is to provide funding for public water pollution control projects through taxation on discharges. Five groups of taxable pollutants, with tax rates based on toxicity, have been compiled. Chromium falls in Group 4 and cyanide is found in Group 5; these two groups carry by far the highest tax rates. A few milligrams of these substances in the waste stream can warrant a large monetary fine over a year for a high-volume metal finisher.

Agencies such as the Department of Transportation are strengthening restrictions for shipment of treatment chemicals such as hydrofluoric acid, which is found in many chromate conversion coating formulations. Individual state EPAs may also enact their own restrictions, which could further restrict the use of harmful treatment chemicals. For example, on 24 July 1989, both Massachusetts and Oregon enacted sweeping toxic waste reduction bills (Ref 31). These bills require industries to prepare plans to reduce their use of toxic substances and to recover or reuse toxic materials from their effluents. The Massachusetts Toxics Use Reduction Act sets as a goal a 50% reduction of toxic waste in the state by 1997. Although no one can predict whether the use of chromium compounds and accelerators such as potassium ferricyanide will be completely banned, the trend in legislation is obviously making the search for viable alternatives to the current technology a top priority.

Furthermore, the Environmental Protection Agency (EPA) is scheduled to be elevated to the Cabinet level, with the head administrator assuming the post of Secretary of the EPA (Ref 30). This will attach an even greater significance to the role of the government in enacting and enforcing legislation directed at maintaining a safer environment.

References cited in this section

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