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New Industry Worker Exposure Limit for Styrene

New Industry Worker Exposure Limit for Styrene. George Cruzan, PhD, DABT ToxWorks. Why Have Worker Exposure Limits?. Why Have Worker Exposure Limits?. To Protect Workers How Safe? Or From What Effects?. Why Have Worker Exposure Limits?. To Protect Workers How Safe? Or From What Effects?

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New Industry Worker Exposure Limit for Styrene

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  1. New Industry Worker Exposure Limit for Styrene George Cruzan, PhD, DABT ToxWorks

  2. Why Have Worker Exposure Limits?

  3. Why Have Worker Exposure Limits? • To Protect Workers • How Safe? Or From What Effects?

  4. Why Have Worker Exposure Limits? • To Protect Workers • How Safe? Or From What Effects? • Early efforts – Death or passing out • 1960s-1980s – Serious health effects • 1990s – ongoing – Subtle effects; may be subclinical

  5. Endpoints of Concern • Previous Endpoints • Cancer, permanent organ damage, blindness, deafness, inebriation, incoordination • Newer Additional Endpoints • Decreased visual accuity, Decreased color discrimination, Slight shift in IQ, Decreased hearing

  6. Styrene Endpoints of Concern • Cancer – No consistent evidence • Permanent Organ Damage – No evidence • Blindness – No evidence • Deafness – No evidence • Inebriation - >100 ppm for 8 hrs • Incoordination - >100 ppm for 8 hrs

  7. Newer Styrene Endpoints • Increased Reaction Time (slower response) • Cherry et al, 1980 – No effect up to 100 ppm • Jejaden et al, 1993 – Increased reaction time in workers exposed average concentration of 23 ppm for 5 years

  8. Newer Styrene Endpoints • Increased Reaction Time (slower response) • Mutti et al., 1984 – Increased RT at 50 ppm and higher; NOEL 25 ppm • Triebig et al., 1989 – No effect at average exposure of 18 ppm • Seeber et al., 2009 – No effect up to 50 ppm

  9. Newer Styrene Endpoints • Color Discrimination • 13 studies – many just compare exposed to non-exposed; controls not always valid – e.g., compare RPC workers to medical students • Most report only average exposure, without dose response

  10. Newer Styrene Endpoints • Color Discrimination • compared high (>50 ppm, ave. 93) and low (<50 ppm, aver. 8) – effect in high, but not low exposure group. • Divided into <30 and >30 ppm. Effect in high but not low dose group. • No effect up to 40 ppm (Triebig study)

  11. Newer Styrene Endpoints • Hearing Loss in Workers • hearing loss at 25 ppm (Moller, 1990) • hearing loss at 20 ppm (Morata, 2002) • hearing loss at 40 ppm for 10 or more years (Triebig, 2009)

  12. Newer Styrene Endpoints • Hearing Loss in Animals • Adjusted NOAEL – 251 ppm (4 weeks, 6 hrs/day) • Adjustment factors - 12.5 (interspecies – 2.5, intraspecies - 5 • DNEL – 251/12.5 = 20 ppm

  13. Considerations in OEL • ACGIH TLV = 20 ppm • REACh DNEL = 20 ppm • Reaction time NOEL >25 ppm • Color discrimination NOEL >30 ppm • Hearing loss NOEL = 30 ppm • OEL should be less than NOEL

  14. Recommended OEL • World-wide industry standard recommended at 20 ppm.

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