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AUG 2018

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NEWS 35 CompositesWorld.com 15,000 samples of drinking water, styrene was undetectable in all but a single sample. "We maintain that the scientific basis that OEHHA used to set the very-low PHG for styrene ... is neither appropriate nor scien- tifically supportable ... because research available to OEHHA at the time it established the PHG indicates that finding of lung tumors in mice — but not in rats or humans — exposed to styrene is not relevant to human risk assessment," explains Ray Ehrlich, SIRC executive director. "is view is similar to the conclusion reached by the EU and several other regulatory agencies." (See Learn More.) Two other organizations that potentially could impact percep- tions about styrene's potential health impacts include the American Conference of Governmental Industrial Hygienists (ACGIH, Cincinnati, OH, US) and the International Agency for Research on Cancer (IARC, Lyon, France), part of the World Health Organization (WHO). Earlier this year, an ACGIH committee announced it might recommend reducing its 8-hour exposure limits for styrene to 2 ppm; ACGIH has stated it will determine how to respond to its committee's recommendation by year's end. ACGIH sets suggested workplace exposure limits, or threshold limit values (TLVs), for certain chemicals. e TLVs, along with other information, are intended to be used by industrial hygien- ists to guide worker-protection efforts. "If a state uses the proposed TLV guidelines when setting its own standards, then this could affect the industry," says Fletcher Lindberg, marketing VP at resin manufacturer AOC LLC (Collierville, TN, US), as well as current chair of SIRC. "However, right now we don't know what kind of impact the change might have, if any, or if the proposed reduction will be adopted by ACGIH." e ACGIH's recommended limit on styrene isn't binding, he notes, but it could eventually be used by insurance carriers when writing policies for manufacturers. "In the short term, it may have limited impact, although it does suggest that the trend will be toward more rules and regulation for styrene in the future," Lindberg adds. At its March 2018 Monograph meeting, IARC upgraded its clas- sification of styrene from Group 2B ("possibly carcinogenic to humans") to Group 2A ("probably carcinogenic to humans"). However, a full report on the IARC Monograph, which will include the panel's rationale and decision to reclassify, will not be avail- able until 2019. "[Like NTP], IARC classifications are based on hazard assessments, not risk assessments," explains Ehrlich. "So, IARC classifications are not indicators of real-world potential risk. e mere presence of, or exposure to, a chemical is not an indica- tion of risk or potential harm." SIRC contends IARC's upgraded classification is not supported by a complete review of the avail- able science. "e safety profile for styrene has not changed," Ehrlich adds. "IARC Monographs have limited utility for national regulators. However, some states do reference IARC classifica- tions when making their own regulatory determinations." Ehrlich says SIRC opposes any classification of styrene based on a hazard assessment only, rather than a quantitative risk assessment because hazard assessments are typically based on findings arising from extreme conditions that do not represent typical use or Finding and offering alternatives Significant work over the past decade by SMC resin suppliers and compounders has been devoted to reducing resin styrene content, finding alternative diluents to replace styrene in whole or in part, to switching from solvent-based to hot-melt compounding systems, and/or to using resin matrices other than vinyl ester and unsaturated polyester. The result is a range of SMC product options for customers in a variety of industries should regulations on styrene be tightened further. In this photo, Laura Littlejohn, scientist at Ashland LLC (Columbus, OH, US), uses thermogravimetric analysis (TGA) to measure weight changes at temperature and over time in SMC samples to evaluate composition analysis and thermal stability. Source | Ashland LLC Styrene-free alternatives Another way SMC resin suppliers and compounders are responding to concerns about tighter styrene limits is by switching to alternative resin systems. One example is the LYTEX SF family of SMC grades from A. Schulman Inc.'s Quantum Composites portfolio (Bay City, MI, US), which uses epoxy instead of vinyl ester or unsaturated polyester. Available reinforced with either chopped carbon fiber or glass fiber, the resins are styrene-free, low-VOC and low-odor. The company reports the materials are simple to process (reducing system costs) yet offer excellent surface appearance and outstanding thermo-mechanical properties, making them ideal for lightweighting solutions. Source | A. Schulman Inc. Styrene Reduction Update

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