Document VJ4XV6VwpQnaqKj1mGYE6yOzN

ViAjl UllOCitfij Government Federal Alert-- new legislation High-dose inhalation cancer tests suggested A new study conducted by and for the federal government concludes that inhaling a single large dose of a known carcinogen can cause cancer in one species of laboratory animal. The report goes so far as to suggest that short-term, high-dose laboratory studies of other known carcinogens "may be appropriate for government and private researchers." Conducted for the Consumer Product Safety Commission, the $700,000 research project examined the effects on rodents of inhaling doses as high as 50,000 ppm of vinyl chloride, a known liver carcinogen. Previously, most inhalation-based carcinogenicity studies with animals have involved comparatively small doses of chemicals given routinely over relatively long periods of time. The current study was performed by Dr. Bernard McNamara and coworkers at the Chemical Systems Laboratory at the U.S. Army Aber deen Proving Grounds in Maryland. Started in 1975, the vinyl chloride study exposed groups of mice and rats to single one-hour doses of vinyl chloride gas in air of 50,000,5000,500, 50, and 0 (controls) ppm. In addition, other groups of the rodents were given 10 one-hour exposures to 500 ppm vinyl chloride five days per week for two weeks. Yet another group of the animals received 100 one-hour exposures to the chemical at 50 ppm, five days per week for 20 weeks. All were then kept in cages for the re mainder of their lives, usually about two years. A reproduction study conducted simultaneously, however, failed to detect any mutagenic or carcinogenic effects in succeeding generations of rodents whose forebears had been exposed to vinyl chloride vapors. But the carcinogenicity study, particularly the single-exposure ex periments, seems to be the focus of study. Several important points arose from the study. For example, only mice and not rats demonstrated any carcinogenic effects from one expo sure to vinyl chloride. And the sin gle-dose experiments produced only adenomas, or benign tumors, gener ally at the highest single-dose levels, virtually all of which subsequently failed to progress to carcinomas, or malignant tumors. Moreover, and perhaps more im portant, the report notes that pneu monitis, a condition of acute, local ized lung inflammation, "was evident in all animal (mice) groups exposed to vinyl chloride in doses of 500 ppm or more." Most toxicologists believe that a dose of a chemical that makes an animal acutely ill should not be used in a carcinogenicity study because it can produce results unrelated to a compound's cancer-inducing poten tial. Specifically, the study found that nearly 33% of the mice exposed to 50,000 ppm of vinyl chloride for one hour developed adenomas of the lung; about 17% of the mice exposed to 5000 ppm also developed adenomas; at 500 ppm 13%, and at 50 ppm 10.1%. By contrast, 10.0% of the animals used as controls (no exposure) de veloped adenomas. Progression to carcinoma, the re port notes, "was minimal" among the mice. Only three of the 137 mice (2.2%) exposed to 50,000 ppm of the plastic monomer later developed carcinoma of the lung. At lesser doses a barely perceptible increase in car cinomas was found. For example, at the next lowest dose of 5000 ppm of vinyl chloride for one hour, one mouse out of 143 (0.7%) eventually devel oped a pulmonary carcinoma. All of which leads to skepticism among industrial toxicologists. Dow Chemical toxicologist Perry Gehring, for instance, says that because of the high level of pneumonitis among the test mice, "the relevance of the results is highly questionable." He notes, too, that only mice and not rats were af fected by the vinyl chloride exposure. "Adenomas in the lungs of mice," Gehring says, "have a very high spontaneous background," particu larly when the mice are in physiolog ically stressful situations such as nearly being anesthetized by vinyl chloride gas. Yet the Consumer Product Safety Commission in releasing the study concludes that its "findings further support the thesis that a single ex posure to a high dose of vinyl chloride, or perhaps other similarly acting carcinogens, could pose a risk of can cer to humans." Dow's Gehring ob serves that long before vinyl chloride was recognized as a liver carcinogen in the early 1970's, "we kne' / that 3000 ppm or higher levels were not uncommon--we should have tumors all over the place [now.]" '' This C&EN report lists new lee islation introduced between March 19 and April 25. Senah and House bills are listed undo areas of interest by bill number primary sponsor, and the com mittee (s) to which it has been re ferred. SENATE Energy. S. 857, 858, 859--Hart (D.-Colo ) ; Provide tax credit for oil produced frorr i shale, regulate surface mining of oil shale. set environmental standards for oil shale > operations; referred to Finance, Environmen ' & Public Works, Energy & Natural Re soirees. . Nuclear. S. 742--Percy (R.4II.). Sets up nev, federal panels to coordinate nuclear waste management programs, details procedure; for state participation in decisions on sitinc of such waste repositories; held at desk. S. 797--Jackson (D.-Wash.). Allows De partment of Energy to take title to spen commercial reactor fuel, construct facilities for its storage; referred to Energy & Natura Resources* , S. 798--Hart (D.-Golo.). Sets up Nuclea; Regulatory Commission licensing proce -tires for away-from-reactor storage of spen fuel; referred to Environment & Public Works* S. 926--McGovern (D.-S.D.). Suspends foi .- three years granting of future nuclear powei ' plant operating licenses, pending review o' - existing, potential safety defects; referred tc k Environment & Public Works. ' R&D. S. 700--Danforth (R.-Mo.). Gives ^corporations a 10% tax credit for ever> dollar spent on R&D; referred to Finance Chouse Energy. H.R. 3749--Murphy (D.-N.Y.). Set; ~ federal standards for siting, construction operation of liquefied gas facilities in or nea: the coastal zone: referred to Merchant Ms . rine & Fisheries, Interstate & Foreign Com , merce. , Environment. H.R. 3247--Hance (D.-Tex.) Allows federal pre-emption of state law: hindering building of the crude oil pipeline b> Sohio between Long Beach, Calif., an; ; Midland, Tex.; referred to Interior & Insula Affairs, Interstate & Foreign Commerce ; Health. H.R. 3132--Holuman (D.-N.Y.) Establishes interim occupational safety ' health standards to protect employees fron , nonionizing radiation; referred to Educatior . & Labor. H.R. 3566--Hammerschmidt (R.-Ark.). Ex * tends moratorium on possible saccharin bat ' by FDA from 18 to 36 months; referred tt Interstate & Foreign Commerce. Nuclear. H.R. 3283--Atkinson (D-Pa.) Prohibits utilities from passing on repai , costs and cost of buying substitute powe ' when nuclear power plant is shut down fo safety reasons; referred to Interstate & Foi eign Commerce. a Administration bill. 14 C&EN Mav 7. 1979 CUSAROSS 02424