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Quality Branch, Ottawa, Ontario, 1979; Vol 1. (46) Raspor, B. In “Cadmium in the Environment”; Nriagu, J. O., Ed.; Wiley: New York, 1980; Vol. I, pp 147-236. (47) Nriagu, J. 0.;Gaillard, J.-F. submitted for publication. (48) Harvey, H. H. In “Ecological Impact of Acid Precipitation”; SNSF Project: Oslo, Norway, 1980; pp 93-98. (49) Dillon, P.; Yan, N. D.; Scheider, W. A.; Conroy, N. I. “Acid Lakes in Ontario: Characterization,Extent and Responses to Base and Nutrient Additions”; Ontario Min. Environ., 1977. (50) Kemp, A. L. W.; Thomas, R. L.; Wong, H. K. T.; Johnston, L. M. Can. J . Earth Sci. 1977, 14, 2402-2413. (51) Snodgrass, W. J. In ”Nickel in the Environment”; Nriagu, J. O., Ed.; Wiley: New York, 1980; pp 203-274. (52) Florence, T. M.; Batley, G. E. Crit. Rev. Anal. Chem. 1981, 9, 219-296. (53) Chau, Y. K.; Wong, P. T. S. In ”Toxicity to Biota of Metal Forms in Natural Waters”; Int. Joint Commission on the Great Lakes; Windsor, Ontario, 1976; pp 187-196. (54) Ontario Ministry of the Environment, Report on “Air Quality Assessment Studies in the Sudbury Area”; Toronto, August 1978; Vols. I and 11. (55) Kramer, J. R. “Fate of Atmospheric SO2 and Related Substances as Indicated by Chemistry of Precipitation”; Department of Geology Report, McMaster University, Hamilton, Ontario, 1976. (56) Jeffries, D. S.; Snyder, W. R. Water, Air, Soil Pollut. 1981, 15, 127-152.
(57) Evans, R. D.; Rigler, F. H. Environ. Sci. Technol. 1980,14, 216-218. (58) Nriagu, J. 0. In “Biogeochemistry of Lead in the Environment”; Nriagu, J. O., Ed.; Elsevier: Amsterdam, 1978, pp 137-184. (59) Nriagu, J. 0. Nature (London) 1979,279, 409-411. (60) Landing, W. M.; Feeley, R. A. Deep-sea Res., Part A 1981, 28,19-37. (61) Balistieri, L.; Brewer, P. G.; Murray, J. W. Deep-sea Res., Part A 1981,28, 101-121. (62) Meyers, P. A.; Bourbonniere,R. A,; Takeuchi, N. Geochim. Cosmochim. Acta 1980, 44, 1215-1221. (63) Berner, R. A. “Early Diagenesis”; Princeton University Press, Princeton, NJ, 1980. (64) Likens, G. E. In “Primary Production of the Biosphere”; Leith, H., Whittaker, R. H., Eds.; Springer-Verlag: New York, 1975; pp 185-202. (65) Glooschenko, W. A.; Moore, J. E.; Munawa, M.; Vollenweider, R. A. J . Fish. Res. Board Can. 1974,31, 253-263. (66) Shaw, D. M.; Dostal, J.; Keays, R. R. Geochim. Cosmochim. Acta 1976, 40, 73-83. (67) Hyne, N. J. Environ. Geol. 1978, 2, 279-287. (68) Hutchinson,T. C. In “Copper in the Environment”;Nriagu, J. O., Ed.; Wiley: New York, 1979; p 451-502.
Received for review July 20,1981. Revised manuscript received February 23, 1982. Accepted April 12, 1982.
Leaching of Cadmium from Pigmented Plastics in a Landfill Site David C. Wilson, Peter J. Young,” Brinley C. Hudson, and Grant Baldwln
Waste Research Unit, Harwell Laboratory, Oxfordshire OX1 1 ORA, England Following concern over cadmium release to the environment, which has caused a ban on most cadmium-containing products in Sweden since July 1982, a two-phase study was undertaken of the leaching of cadmium from pigmented plastics disposed to landfill. Subjection of several pigmented plastics and related materials to a small-scale standardized leaching test indicated low cadmium releases and suggested that kinetic factors control leaching. Several column validation experiments were performed with pulverized domestic waste and a “worstcase” plastic; these demonstrated that pigmented plastics make an insignificant contribution to cadmium levels in domestic waste leachate. Concentrations up to 45 pg of cadmium/L were highest from refuse alone, and all peak levels were delayed, corresponding in practice to about 10 years. The conclusion is that landfill is an acceptable disposal option for cadmium-pigmented plastics and that it does not result in a significant release of cadmium to the environment. Introduction
Concern has recently increased about the possible harmful effects of cadmium released to the environment. Both the causes and the effects of cadmium accumulation in human tissue are still subjects of much scientific controversy. Nevertheless, political moves have already begun to combat this accumulation: the Swedish government has led the way by announcing a ban on the production and import of (most) cadmium-containing products, originally effective January 1,1980, but since postponed until July 1982. The rationale for this ban on consumer products is that all such materials eventually end up in municipal waste, and the cadmium thus causes pollution either in 560
leachates draining from landfill sites or as off-gases from incinerators. One of the major product groups affcted by the Swedish ban is cadmium-pigmented plastics. The Waste Research Unit of the Harwell Laboratory was commissioned by Blythe Colours Ltd., on behalf of a group of European pigment producers under the auspices of the European Federation of Chemical Industries Associations (CEFIC), to provide an independent and unbiased technical assessment of the environmental problems likely to be caused by cadmium-pigmented plastics as a component of municipal wastes in landfill sites. This paper reports the findings of that investigation. Depending on the country, 20-40% of total cadmium usage is accounted for in pigments (1,2).These pigments can be produced in brilliant yellows, from cadmium sulfide or cadmium-zinc sulfides, and in oranges and reds, from cadmium sulfide-selenium mixtures. The chemicals are calcined at temperatures of 600-700 “C and ground to produce fine particles of pigment and are generally nonstoichiometric in composition. About 80 % of cadmium pigments are used in plastics ( 3 ) ,both expense and environmental factors restricting their use to high-grade special plastics with high processing temperatures and high performance specifications, where there is no effective substitute ( 4 ) . Styrene copolymers, particularly acrylonitrile-butadiene styrene (ABS), and high-density polyethylene account for 85% of cadmium pigments in plastics, which corresponded to about 2500 tons of pigment in Europe in 1976 (3).Minor uses include synthetic leather from PVC, where excellent resistance to migration is required. However, stabilizers are a more important source of cadmium in the case of PVC, whose manufacture re-
Environ. Scl. Technol., Vol. 16, No. 9, 1982 0013-936X/82/0916-0560$01.25/0
Published 1982 by the American Chemical Society
quires the bulk of all stabilizers. About 20-30% of the stabilizers are barium-cadmium based, used for outdoor applications of PVC, and the principal chemicals of interest are cadmium stearate, octanoate, and palmitate. Where such stabilizers are used in PVC, they give rise to about 250 mg of cadmium/kg, but averaged over all plastics (containing 20-30% PVC) cadmium derived from stabilizers is only 10-15 mg/kg. This compares with an average cadmium contribution from pigments of around 25 mg/kg since of the 5% of all plastics that are colored, about half contain 0.01-1 % cadmium due to the pigment. Plastics comprise between 1% and 10% of municipal waste in most countries, with an average in the developed western world of perhaps 5%, and absolute maximum recorded values of 13% in parts of Japan and Sweden (5, 6). Plastics thus contribute about 2 mg of cadmium/kg of municipal waste, out of a total cadmium concentration often taken as about 12 mg/kg (7). Perhaps 1-2 mg/kg can be attributed to trace levels in items such as paper, fine material, putrescibles, and vegetable matter. The balance is due to cadmium present in zinc products and to other cadmium-containing products such as batteries or plated metals. In order to extrapolate the test results to the field situation, we will assume a worst case of refuse containing 15% plastic, of which 2.5% contains cadmium as pigment; thus 1t of waste contains about 4 kg of pigmented plastic. The results derived here for cadmium in leachate attributable to pigmented plastics may be placed in context by comparison with both observed concentrations and “standard” levels set to protect water quality. Cadmium levels in domestic waste leachate vary widely; two recent compilations suggest a range of
