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Worries growing over use of cadmium.

Worries Growing Over Use of Cadmium

Renewed concern has risen among additives makers and users regarding pigments and PVC heat stabilizers based on cadmium, a heavy metal suspected of causing cancer and kidney disease. As public pressure mounts over possible health risks linked to cadmium, an increasing number of high-profile companies are vowing to curtail their reliance on it. Some have already eliminated cadmium compounds from their products. Others are beginning to buckle under the pressure and have begin exploring alternatives to cadmium.

The latest search for replacements, suppliers and users agree, is a direct result of a recent wave of regulatory proposals that could affect the future of the metal's use in plastics. Among the pending government actions are:

* A concerted effort by nine Northeastern states to limit the amount of heavy metals used in packaging;

* More stringent OSHA standards regulating exposure to cadmium;

* The first upgrade of the Clean Air Act in more than a decade, which could include rigid emissions standards for cadmium.


The Coalition of Northeastern Governors (CONEG), a Washington, D.C.-based group representing the nine states of Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island and Vermont, has drafted legislation to be introduced in each state to reduce the amount of four heavy metals--cadmium, lead, mercury and hexavalent chromium--used in pigments and inks in packaging. The proposed legislation calls for packaging manufacturers to reduce the sum of the concentration levels of these metals in their products to 600 ppm two years after the legislation is enacted, 250 ppm within three years, and 100 ppm within four years. The proposed laws provide an exemption for packaging made from recycled materials and for cases where the use of the heavy-metal compounds is essential to the protection, safe handling or function of the package's contents.

Another regulatory move could affect every user of cadmium. Just as we went to press, OSHA issued a pair of alternative proposed limits on exposure to airborne cadmium, which would reduce allowable limits by 95-99% from the current 200 micrograms/cu meter. The alternative proposals include 8-hr time-weighted average exposure limits of 1 and 5 [mu]g/cu m, 15-min excursion limits of 5 and 25 [mu]g/cu m (respectively), and action levels of 0.5 and 2.5 [mu]g/cu m. OSHA is seeking industry's comments, since the agency intends to finally adopt just one standard. the lower limit would require greater use of respirators and would cost industry more to adopt. The proposed standard also contains provisions on exposure monitoring, medical surveillance, recordkeeping, hazard communication, and more. Informal hearings will be held on the proposals June 5 in Washington, D.C., and July 17 in Denver. If the preliminary levels are established this year, final standards could be in place sometime in 1991, industry sources say. The pigment industry has been providing the agency with data supporting separate and higher limits for cadmium in insoluble pigmentary form.

While the OSHA standards are designed to protect those inside factories using cadmium, pending EPA standards could protect those outside the plants. When the EPa announced its plans for 1990, an investigation into the need for regulation of cadmium emissions into the air was among its priorities. (See PT, Feb. '90, p. 103). If the regulatory agency finds the need for emission standards, they will be included in the reauthorization of the federal Clean Air Act, expected to be passed by Congress this year. The revised law, which President Bush has repeatedly said he supports, would tighten restrictions on hundreds of substances and set fresh guidelines for others, including cadmium-containing gases allegedly released into the atmosphere by the incineration of cadmium-containing plastic waste.


Although there has been recurring talk of replacing cadmium-based additives for more than a decade, these latest proposals coupled with an eight-fold escalation in cadmium metal prices over the last two years have brought the debate back into the spotlight.

"It's in vogue now to jump on cadmium," says Mitchell Silkotch, market development manager for thermoplastic additives at Akzo Chemicals, Chicago, which just recently came out with some new non-cadmium stabilizers (see New Products section). "Cadmium has gotten some bad press and because of that we're going to see a decline in its use in coming years." One other m ajor producer of cadmium heat stablizers told PLASTICS TECHNOLOGY confidentially that it is planning ultimately to discontinue such products. And The Vinyl Institute, an industry organization in Wayne, N.J., recently decide that it would support a public statement to be issued as early as this month by SPI's Council for Solid Waste Solutions, Washington, D.C., which would call for a reduction in the amount of cadmium used in all plastic packaging.


As public outcry grows over suggestions from environmentalists that incinerating cadmium-containing plastics is producing toxic ash that can contaminate groundwater, lawmakers have responded with a rash of proposals such as those mentioned above. In turn, some processors have told suppliers that they will phase out their use of cadmium colors. On the other hand, some vinyl formulators complain that they are being pressured more by their stabilizer suppliers to replace cadmium than by the customers.

Last year, Mobay Corp.'s Plastic and Rubber Div. in Pittsburgh and GE Plasics in Pittsfield, Mass., were among a handful of companies that announced their intention to become cadmium-free. Meanwhile, others such as B.F. Goodrich Co., Cleveland; SCM Chemicals Inc., Baltimore; Heubach, Inc., Newark, N.J.; Dow Chemical Co., Midland, Mich.; Synthetic Products Co., Cleveland; and Argus Div. of Witco Chemical, N.Y.C., have not sworn off cadmium but are moving to either curtail its use or develop alternatives.

For Mobay, which said in May that it would be cadmium-free before the start of this year (see PT, July '89, p. 110), the move away from the heavy metal required reformulating more than 2000 colors in its line of eight engineering resins. In late December, a spokesman at Mobay said the company had met its target date and was about to enter the 1990s "free of cadmium."

Last fall, Ge Plastics, Pittsfield, Mass., broadened a policy begun in January 1988 to eliminate cadmium and heavy metals from its pigments. Initially, the plan called for heavy-metal-free colorants for new color matches in all except automotive applications, since it was felt that only heavy-metal pigments could satisfy the stringent accelrated light aging requirements on these plastics. In November, the policy was expanded to include auto uses.

"We are seeing some problems already," said Joseph M. Cameron, GE's divisional color manager. "Since we have had to substitute organic pigments that tend to be more transparent, some of the automotive colors are less than completely satisfactory."

Complicating GE's quest is a reluctance by its customers to settle for duller colors formulated with non-cadmium pigments. "Our customers don't appear to be as interested in doing away with cadmium as we are," sais Michael Burzminski, GE's manager of divisional quality and color. "This has led to a situation where we may still use cadmium on a rare case-by-case basis for those who demand it, such as the auto industry, which wants those bright colors for car interiors."

SCM Chemicals, while not abandoning cadmium, is developing a manufacturing process that will lower the acid-soluble portion of cadmium in its pigments to a level below the EPa toxicity limit while maintaining the same bright colors cadmium has always provided. "We still have a way to go," says SCM spokesman Louis Kistner, "but our preliminary indications are very promising."

To some extent, the regulatory pressure is growing on lead-based compounds, as well. William J. windscheif, director of polymers business development for Vista Chemical Co., Houston, says his firm recognizes that it will eventually need to replace the lead stabilizers used in many of its rigid PVC siding and window-profile compounds. While there are readily available organotin alternatives, he notes that there are no satisfactory alternatives for wire and cable coatings--the most common use of lead stabilizers.


While some view the move away from cadmium and the search for safer alternatives as environmentally sound, others see it as nothing more than a public relations ploy to counteract the "bad guy" image frequently associated with chemical manufacturers. Cadmium, they say, is essential to the future of colored plastics. "There is a core of uses for cadmium pigments and in that core, there are no replacements," says Leonard J. Ulicny, chairman of the Cadmium Pigment Committee of the Dry Color Manufacturers' Association, Alexandria, Va. Ulicny says cadmium pigments provide benefits unattainable with any alternative. He points to cadmium's lightfastness, high heat stability (up to 1000 F in some cases) and the deep, rich colors ranging from bright yellows and oranges to reds and maroons it provides as evidence of its value. Furthermore, he says plastics containing cadmium-based pigments are ideal for recycling since they retain their color better than plastics containing non-cadmium-based colorants.

Proponents of cadmium say environmentalists' pictures of cancer-causing clouds spewing from incinerator smokestacks and toxic waste leaching from landfills into groundwater is an unreal scenario, designed to frighten the industry into curtailing its use of cadmium. "The furor that is going on today is not based on fact," argues Robert A. Charvat, director of color application technology and market development for Engelhard Corp.'s Specialty Minerals and Colors Div., Beachwood, Ohio. "It's based on emotion and politics, not on good science."

The cadmium pigments used to color plastics are safe, supporters say, because unlike pure cadmium, the high-temperature calcining process that produces the pigments renders the compounds insoluble and difficult to break down into their base elements. Research by the Cadmium Council, a trade group in Greenwich, Conn., has shown that insoluble forms of cadmium in pigments are not able to be absorbed by animals' digestive systems.

Speaking at an SPE Color and Appearance Div. RETEC in Huron, Ohio, last fall, Demetra Balmer, occupational health and safety chemist for Ferro Corp.'s Color Div., Cleveland, said, "Calcining these pigments at temperatures around 1200 F changes their crystal structure to a hexagonal structure, which locks the cadmium in the crystal and makes the pigments insoluble and biologically unavailable."

"Cadmium sulfide pigments' toxicity potential should be classified based on their own properties, not on those of pure cadmium metal," argues Edwin C. Davenport, sr. v.p. of Whittaker, Clark & Daniels Inc., S. Plainfield, N.J.

The thrust of the growining anti-cadmium sentiment involves burning products made with these compounds. Oponents of cadmium use in plastics--groups such as the Natural Resources Defense Council, the Environmental Defense Fund and the International Chemical Workers Union--say incinerator ash buried in landfills across the nation contains highly toxic cadmium oxide deposits left when the plastic compounds are burned. These deposits, they say, are leaching into water tables that supply drinking water to surrounding residential areas.

But backers of cadmium pigments point to data showing that although exposure to high heat does alter an insoluble cadmium pigment's chemical structure, it doesn't change it so drastically as to allow the cadmium contained in the compound to become soluble and therefore biologically available.

The organic cadmium salts used as vinyl stabilizers are another matter altogether. These are indeed soluble, and therefore the question of potential toxicity cannot be dismissed as easily in their case.

Yet, despite their attempts to refute the health concerns associated with cadmium colorants, supporters of their continued use admit that even the suggestion that cadmium in plastics may be responsible for health hazards could doom its future in this market. "I believe we've already missed the boat on the case for cadmium and lead additives," GE's Joe Cameron said at the Color and Appearance Div. RETEC. "I believe the time has passed where we can debate their safety. Cadmium is a definite problem if it becomes soluble cadmium, and we have a lot of evidence that points to that happening when the plastic is incinerated."


A year ago, the U.S. Environmental Protection Agency issued a 207-page report called "Characterization of Products Containing Lead and Cadmium in Municipal Solid Waste in the United States, 1979 to 2000." The detailed report, done for the EPA by Franklin Associates, Ltd., Prairie Village, Kans., charts the amount of lead and cadmium in municipal trash and garbage. While cadmium-nickel batteries were the leading contributor of cadmium to solid waste, plastics containing both cadmium pigments and stabilizers ranked second, contributing 564 tons of the metal to the waste stream in 1986, the latest year for which statistics are available. That accounts for 28% of total cadmium discarded that year, the report says.

In 1978, plastics were responsible for 595 tons or 38% of total cadmium discards, the highest figure ever for plastic-generated cadmium, the EPA report says. By the turn of the century, the report predicts, 384 tons or 14% of total discarded cadmium are expected to come from plastics.

According to the EPA report, the most common use of cadmium in plastics is for coloring ABS. Approximately 35%, or nearly 200 tons, of the cadmium used in plastics each year is used on this polymer, an estimated 90 tons of which finds its way into municipal landfills and garbage incinerators. HDPE accounts for 25% of the cadmium; PP 15%; and LDPE and PS 10% each. Other plastics, which the EPA believes are mostly PVC, account for the remaining 5%.


If proposed laws and standards are implemented, processors and suppliers say there will be a scramble to find alternatives to cadmium--alternatives, they contend, that will rarely be as good, and in the long run may not be as safe.

"Cadmium pigment itself is not really all that dangerous," Cameron says. "A lot of the things that are being used to replace it are unknown or made from highly toxic ingredients that may prove to be environmentally worse if they are burned."

Possible substitutes for cadmium in pigments include not only organic compounds butinorganics such as iron oxide and a host of nickel titanates blended with antimony. The latter group provides heat stability comparable to that of cadmium, experts say. But the knock against both of these substitutes is their inability to provide the same color shades that can be achieved with cadmium. Use of iron oxide results in a muted reddish-brown color, while the nickel titanates with antimony give poorer color dispersion, compounders say.

For replacing cadmium in PVC stabilizers, suppliers have been offering liquid barium-zinc compounds, which they say provide equal or better performance at an equivalent or occasionally lower price.
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Title Annotation:Additives
Author:Monks, Richard
Publication:Plastics Technology
Date:Mar 1, 1990
Previous Article:Enhanced SPC and production data.
Next Article:Recycling ventures proliferate.

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