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A dose-response curve for yusho syndrome
1Monsanto Company, St. Louis, Missouri 63167.
Regulatory Toxicology and Pharmacology : RTP
|December 1, 1987
Summary
The median dose of polychlorodibenzofurans (PCDFs) causing severe Yusho symptoms was 68 micrograms/kg. A daily intake of 150 pg/kg PCDFs is considered safe for humans.
Area of Science:
- Environmental Health
- Toxicology
- Epidemiology
Background:
- Yusho disease resulted from consuming contaminated rice oil.
- Polychlorodibenzofurans (PCDFs) are suspected causative agents, but co-contaminants like polychlorobiphenyls (PCBs) complicate toxicity assessments.
Purpose of the Study:
- To estimate the median effective dose (ED50) of PCDFs causing severe Yusho symptoms.
- To establish a health-conservative daily intake level for PCDFs to inform environmental standards.
Main Methods:
- Analysis of rice oil consumption in Yusho patients.
- Estimation of PCDF and co-contaminant levels in consumed oil.
- Utilizing existing data on 2,3,7,8-tetrachlorodibenzodioxin (TCDD) clearance rates in humans.
Main Results:
- The estimated ED50 for severe Yusho symptoms from PCDFs was 68 micrograms/kg body mass.
- A safe daily intake level of 150 pg/kg/day for PCDFs was calculated, considering human TCDD clearance.
- This safe intake level is 50-100 times higher than current North American environmental exposure.
Conclusions:
- PCDFs are likely the primary cause of Yusho syndrome.
- A daily PCDF intake of 150 pg/kg/day provides a conservative basis for environmental standards.
- Current environmental PCDF exposure levels in North America are significantly below this safe threshold.