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

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? –Early efforts – Death or passing out –1960s-1980s – Serious health effects –1990s – ongoing – Subtle effects; may be subclinical

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

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

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

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

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

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 ppm. Effect in high but not low dose group. –No effect up to 40 ppm (Triebig study)

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)

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

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

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