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Type of information:
experimental study
Adequacy of study:
weight of evidence
2 (reliable with restrictions)
Rationale for reliability incl. deficiencies:
other: see 'Remark'
Experimental data was reviewed by the ECETOC Task Force, author of the JACC Report No. 53, "Cyanides of Hydrogen, Sodium and Potassium, and Acetone Cyanohydrin (CAS No. 74-90-8, 143-33-9, 151-50-8 and 75-86-5)", 2007. The report is a weight of evidence approach to an extensive body of literature, much of which was undertaken prior to development of guildelines. The report was peer reviewed by the scientific non-governmental organization (NGO), which judged the data to be reliable with restrictions.

Data source

Reference Type:
Thyroid function in a cassava-eating population affected by epidemic spastic paraparesis.
Cliff J, Lundquist P, Rosling H, Sobro B, Wide L.
Bibliographic source:
Acta endocrinologica 113: 523-528

Materials and methods

Study type:
biological effect monitoring
GLP compliance:

Test material

Constituent 1
Chemical structure
Reference substance name:
Hydrogen cyanide
EC Number:
EC Name:
Hydrogen cyanide
Cas Number:
Molecular formula:
hydrogen cyanide


Type of population:
Details on study design:
This is a study of people of Mozambique where cassava root, containing cyanogenic glycosides, is eaten in the diet.

Results and discussion

Cliff et al (1986) studied thyroid function in a rural population in Mozambique that had been affected by an epidemic of spastic paraparesis reportedly attributed to dietary cyanide exposure from cassava. Levels of serum (250 μmol/l) and urinary thiocyanate (132 mmol/mol creatinine, corresponding to 1,137 μmol/l) were recorded for a sample of this population, indicating significant exposure to cyanide. Urinary excretion of iodine was within normal limits, indicating adequate dietary intake of iodine. The serum levels of the free T4 index were decreased and the serum free T3 index, T3/T4 ratio and TSH levels were raised. However, serum TSH values were all below 10 mU/l, indicating that no one had severe hypothyroidism. Only 3 subjects had enlarged goitre glands. This hormone pattern was suggestive of an adaptation to the antithyroid effect of thiocyanate, but not overt hypothyroidism (prevalence 1.1%). A follow-up study on school children also demonstrated high urinary thiocyanate levels, adequate intake of iodine, and absense of endemic goitre. The authors suggested that if iodine supply was adequate, the thyroid gland was capable of adaptation to a heavy body burden of thiocyanate without development of overt hypothyroidism or goitre. The authors mentioned that the serum thiocyanate levels in this study were higher than those reported by other researchers (Bourdoux et al, 1978).

Applicant's summary and conclusion

In cassava-eating populations of rural Mozambique, Cliff et al. found very high thiocyanate levels in serum, but almost no goitre (1.1%), probably due to an adequate iodide supply. The authors concluded that the Mozambique population had adapted to the heavy thiocyanate exposure and that adequate iodide intake, in addition to the adaptation, had protected against the goitrogenic effects of thiocyanate.