Endemic selenium intoxication of humans in China.
Level 4 - case-series / case-control
Descriptive outbreak investigation, environmental exposure assessment, and case series
PubMed 6846228 · doi:10.1093/ajcn/37.5.872
What was done
Investigators evaluated an endemic outbreak of selenium intoxication discovered in 1961 in Enshi County, Hubei Province, China. The investigation documented morbidity among 248 inhabitants across five heavily affected villages during peak years (1961–1964), detailed a fatal case in a middle-aged female with hemiplegia, measured post-peak daily dietary selenium intake, and analyzed selenium concentrations in biological samples (blood, hair, urine) and environmental sources (coal, soil, crops) compared to selenium-deficient (Keshan disease) regions.
What was found
Morbidity was nearly 50% among the 248 residents during 1961–1964, presenting predominantly as loss of hair and nails, alongside skin, nervous system, and potential tooth lesions. Post-peak daily dietary selenium intake averaged 4.99 mg (range: 3.20 to 6.69 mg). Mean selenium levels were 32.2 micrograms/ml in hair and 3.2 micrograms/ml in blood. Biological and environmental selenium levels differed by up to 1,000-fold compared to Keshan disease areas. The environmental source was stony coal averaging over 300 micrograms/g selenium (one sample exceeded 80,000 micrograms/g), which entered crops via weathered soil and lime fertilization during a drought that forced higher intake of high-selenium vegetables and maize.
Why it matters
This investigation provides seminal clinical and environmental benchmark data on human selenosis, defining the symptomatic manifestations, biomarker concentrations, and intake thresholds associated with severe dietary selenium poisoning.
Limits
Dietary intakes were estimated retrospectively after the peak outbreak subsided rather than measured during the acute intoxication phase. The report relies on descriptive aggregate prevalence and single-case narrative without formal comparative inferential statistics or longitudinal neurological assessments.
Cited by
- supports Excessive selenium intake can cause hair loss and brittle nails.