The Chemical World This Week
ETHYLENE DIGHLORIDE CANCER ISSUE HEATS UP A controversy over the carcinogenic potential of ethylene dichloride may be about to come to a boil. This week, the National Cancer Institute is releasing a detailed report on its carcinogenesis bioassay that determined that ethylene dichloride is carcinogenic to rats and mice. Meanwhile, the chemical industry is awaiting final results from a study sponsored jointly by the U.S. industry, administered by the Manufacturing Chemists Association, and by European industry. The joint study is being carried out by Dr. Cesare Maltoni of the University of Bologna, Italy. A status report by Maltoni last May concluded that on the basis of present data and under the conditions of his study, ethylene dichloride has failed to show specific carcinogenic potential. First results of the NCI study came out about a year ago and the study was reviewed and accepted by NCTs Clearinghouse on Environmental Carcinogens last March. On the basis of the study, the National Institute for Occupational Safety & Health recommended a reduction in the still-current Occupational Safety & Health Administration standard of 50 ppm (eight-hour time-weighted average) to 5 ppm (time-weighted average for up to a 10-hour workday, 40-hour workweek). Even this standard may not be low enough, the NCI study suggests.
Ethylene dichloride at a glance Production capacity — More than 14 billion lb Production, 1978 -Estimated 10.5 billion lb Capacity use About 7 3 % Production growth- None from 1977, 8 % per year over past decade Merchant s a l e s - A b o u t 17% of production, rest used captively Uses- Vinyl chloride, about 8 0 % Chlorinated solvents, about 10% Lead scavenging and other, 10% Price- About 11 cents a lb at plant Value About S 1.1 billion for total production Producers Continental Oil, Diamond Shamrock, Dow Chemical, Ethyl, B. F. Goodrich, ICI Americas, PPG Industries, Shell Oil, Stauffer Chemical, Union Carbide, Vulcan Materials
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C&ENSept. 25, 1978
However, U.S. company sources say they are monitoring plants carefully and the 50-ppm limit is low enough, given the apparent confusion in test results to date. Ethylene dichloride customers also have been informed fully of the safety question. The two studies bring up anew the controversy over the significance of testing conditions. The NCI study was carried out by administering the chemical mixed in corn oil to rats and mice by gavage (stomach tube) for 18 months. The Maltoni study administered the chemical by inhalation seven hours daily, five times weekly, for 18 months. Actually the question of ethylene dichloride safety is mainly a problem for a relatively few major users of the material, the 15th largest-volume U.S. commercial chemical. Most ethylene dichloride is converted in nearby plants to vinyl chloride, the raw material for polyvinyl chloride. About 83% of ethylene dichloride never leaves the producing company. And at least 90% of the chemical is converted immediately to other chemicals such as vinyl chloride and chlorinated solvents. Very little is sold for use as ethylene dichloride. In its bioassay, NCI determined that, in male rats, the chemical causes cancer of the stomach, spleen, and other organs, as well as subcutaneous cancers. It causes mammary cancers in female rats and mice and uterine cancers in female mice. And it causes lung cancer in male and female mice. The NCI-contracted study, conducted by Hazelton Laboratories America, Vienna, Va., was carried out using 50 male and 50 female Osborne-Mendel rats and 50 male and 50 female B6C3F1 mice for each of two dose levels of ethylene dichloride. Groups of 20 rats and mice of each sex were used as vehicle controls and given corn oil alone. And groups of 20 of each species and sex were untreated controls. Because of changes in dosages during the study, dosages were later calculated as time-weighted averages. For high-dose male and female rats, the average dose was 95 mg per kg per day and the low dose 47. In male mice, the average high dose was 195 mg per kg per day and low dose 97. In female mice, the average high dose was 299 mg per kg per day and low dose 148.
In the Maltoni study rats and mice were exposed to 250 ppm (later lowered to 150 because of acute toxicity), 50 ppm, 10 ppm, and 5 ppm ethylene dichloride. Maltoni has reported that no "specific" type of tumor was found in rats and mice, although there was a moderate overall increase in benign mammary tumors in rats. D
New method devised for coal desulfurization The use of limestone to remove sulfur from coal chemically has heretofore been restricted to fluid-bed combustors. But a new process for extending this desulfurization technology to more general use has been developed by McDowell-Wellman Co., a subsidiary of Helix Technology Corp., Waltham, Mass. The new process yields small pellets of coal containing limestone and other ingredients, which McDowellWellman doesn't specify. The pellets retain sulfur, presumably as a sulfate, during the combustion, much like limestone in a burning fluid bed. According to McDowell-Wellman vice president Donald Sheppard, the pellets retain their integrity during combustion and can be removed without breaking down to fly ash. Although there may be some mineral value in the burned pellets, it isn't considered crucial to the market success of the fuel. The pelleting process has been under development for the past 18 months and has been tested with several kinds of Ohio coal. The development has been a joint venture between McDowell-Wellman and the Ohio Department of Energy. At present, McDowell-Wellman is considering a number of possible options for marketing the process. One, Sheppard says, is setting up wholly
C&EN's New York office moves The New York News Bureau of Chemical & Engineering News has moved. The new address is 405 Lexington Ave. (Chrysler Building), New York, N.Y. 10017. The new telephone number is (212)697-3223.
