Health- and vegetative-based effect screening values for ethylene

Area of Science:

• Environmental Science
• Toxicology
• Public Health

Background:

• Ethylene (ET) is naturally and anthropogenically produced, with natural sources dominating.
• Concerns about ET toxicity stem from its metabolic conversion to ethylene oxide (EtO), a known carcinogen.
• ET affects plant species at lower concentrations than those adverse to humans.

Purpose of the Study:

• To assess the health and welfare (odor and vegetation) impacts of ethylene (ET).
• To establish health and vegetation-based toxicity factors for ET in accordance with TCEQ guidelines.
• To determine appropriate Effect Screening Levels (ESLs) for air permit reviews and monitoring.

Main Methods:

• Conducted detailed health and welfare-based assessments of ET.
• Utilized well-conducted animal toxicity studies for health assessments.
• Performed a weight-of-evidence evaluation of potential mutagenic and carcinogenic modes of action.

Main Results:

• Health-based assessments yielded higher ESLs than vegetation-based thresholds.
• Metabolic conversion of ET to EtO was deemed insufficient to pose a cancer risk.
• Short-term vegetation-based ESL: 1200 ppb; Chronic vegetation-based ESL: 30 ppb.

Conclusions:

• TCEQ's acute and chronic ESLs for vegetation are protective of public health.
• Vegetation-based ESLs are significantly lower than health-based ESLs, ensuring broader protection.
• The established ESLs safeguard the general public, including vulnerable populations, from adverse effects.