19 May 2011 17:33 [Source: ICIS news]
By Joe Kamalick
A release date for the final report is not yet available, nor is the text of the final analysis of styrene.
However, the most recent draft copy of the report determines that styrene “is reasonably anticipated to be a human carcinogen”.
That level of assessment is lower than the outright “known carcinogen” determination, but the distinction would likely be lost to public perception once the final report is issued.
NTP operates under the National Institutes of Health (NIH), which in turn is part of the Department of Health and Human Services (HHS). The NTP agency has been issuing reports on carcinogens periodically since 1980, and the pending 12th such study covers seven chemicals and substances other than styrene.
In NTP’s “draft substance profile” for styrene it is noted that “there is limited evidence of the carcinogenicity of styrene in humans based on studies of workers exposed to styrene”, showing increased death rates or increased rates of leukaemia or lymphoma or both among plant workers.
Workers in three major industries were studied, according to the report, including the reinforced plastics sector, the styrene-butadiene rubber industry, and the styrene monomer and polymer sector.
“Increased risks for lymphohematopoietic cancers (leukaemia or lymphoma or all) were found among styrene-exposed workers in both the reinforced plastics and styrene-butadiene rubber industries,” the report said.
However, the draft RoC notes, “Causality is not established, as the possibility of confounding from other chemical exposures or chance cannot be completely ruled out”.
Nevertheless, the draft adds, “a causal relationship between styrene exposures and cancer in humans is credible”.
That determination, along with the report’s later characterisation of styrene exposure among the public, could have profound impact on a broad range of manufacturing and products.
As the report notes, about 50% of styrene goes into production of polystyrene, which in turn is “used extensively in the manufacture of plastic packaging, thermal insulation in building construction and refrigeration equipment, and disposable cups and containers”.
“Styrene polymers and copolymers also are increasingly used to produce various house wares, food containers, toys, electrical devices, automobile body parts, corrosion-resistant tanks and pipes, various construction items, carpet backings, house paints, computer printer cartridges, insulation products, wood floor waxes and polishes, adhesives, putties, personal care products, and other items, and they are used in paper processing.”
Given those widespread applications, the report looks at public exposure.
“Styrene has been measured in outdoor air but generally higher levels have been found in indoor air, drinking water, groundwater, surface water, soil, and food,” the draft report says.
“Styrene can be emitted to the air from industrial production and use of styrene and styrene-based polymers and copolymers, motor vehicle emissions and other combustion processes, off-gassing of building materials and consumer products,” the report adds, noting in addition that “Numerous spills containing styrene have been reported to the National Response Center since 1990, and these spills have the potential to contaminate air, water, soil, and food supplies”.
“Studies have shown that food can be a major contributor to styrene exposure for the general population [and] styrene has been detected as a constituent of a wide range of foods and beverages,” the report said.
“The presence of styrene in packaged foods is reported to be due primarily to monomer leaching from polystyrene containers,” the report said, in particular noting that “Styrene was detected in all eight human breast milk samples from women in four
The NTP report takes pains to note that its substance profile on styrene is only a draft, circulated for public comment and “should not be construed to represent final NTP determination or policy”.
Even so, US styrene producers and users are understandably worried.
An alliance of trade groups representing styrene producers and manufacturers dependent on styrene has asked the parent Department of Health and Human Services to delay final publication of NTP’s 12th Report on Carcinogens.
That group, the Styrene Information and Research Center (SIRC), argues that the NTP’s study of styrene is flawed and deficient.
Those charges were reflected in a letter this week from 63 bipartisan members of Congress to Health and Human Services Secretary Kathleen Sebelius, along with warnings of potentially major job losses if styrene is branded as a likely carcinogen.
“We believe that the [RoC] draft runs a strong risk of furthering job uncertainty and confusion across a broad sector of American manufacturing,” the 47 Republican and 16 Democrat representatives said.
“We respectfully ask that you delay issuing the styrene assessment until a thorough review can be conducted that weighs the full body of scientific evidence available,” the letter said.
The representatives charged that NTP’s styrene study lacked proper scientific peer review, failed to respond adequately to public comments and did not consider all relevant scientific data.
They also cited earlier studies by EU scientists who found that styrene was not likely to cause cancer in humans.
The letter said that as many as 775,000 Americans work in styrene production or in the manufacture of styrene-based products, warning that those jobs would be at risk if NTP labels styrene as a likely carcinogen.
The NTP draft report does include a disclaimer saying that the agency “has no opinion about actual health risks posed” by any of the substances listed in the pending report.
“But this will almost certainly not counteract the plain language meaning of the phrase ‘reasonably anticipated carcinogen’,” the members of Congress said.
Joe Walker, spokesman for the styrene alliance, said that the NTP report might be issued within weeks if the delay appeal was not successful.
If styrene is labelled as a likely carcinogen,
Included among those options would be a formal request for review of the NTP study by the National Academy of Sciences (NAS). In addition,
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