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Your Location:Home > What is effects on humans on Thiourea

There are reports on disorders of workers coming into contact with thiourea during the course of, for example, maintenance of machinery or packing, without providing any details as to exposure levels. The symptoms observed were typical of hypothyroidism, as evidenced by facial oedema, hypotonia, bradycardia, electrocardiograph alterations associated with reduced basal metabolism, constipation, flatulence, polyuria, and granulocytopenia, accompanied by lymphocytosis and monocytosis. The first perturbations of the blood count were observed after 5–6 months of exposure, and the highest incidence of the symptoms was evident in those workers who had been in contact with the chemical for 5–15 years (Zaslawska, 1964; Speranski et al., 1969).

Indications of reduced thyroid function were observed in a Russian study of workers employed in thiourea manufacture. The study covered 45 exposed workers and 20 unexposed controls. Reported air concentrations of thiourea were in the range 0.6–12 mg/m3 (see section 6.1). The workers had been exposed for 9.5 ± 1.1 years; 73% had been exposed for at least 5 years; and 54.5% of them were over 40 years of age. The concentrations of thyroid hormones T4 and T3 were significantly lower in the exposed workers than in the controls (T4: 78.0 ± 5.2 versus 109.4 ± 2.0 nmol/litre, P < 0.05; T3: 1.2 ± 0.1 versus 3.8 ± 0.1 nmol/litre, P < 0.001). Thyroid hyperplasia was observed in 17 of the 45 exposed workers. Concentrations of T4 and T3 in this subgroup were 80.6 ± 1.8 and 0.9 ± 0.1 nmol/litre, respectively (Talakin et al., 1985).

Slightly elevated levels of immunoglobulin A (1.2 mg/ml compared with 1.03 mg/ml in controls) and immunoglobulin M (1.4 mg/ml compared with a control value of 0.91 mg/ml) were determined for workers in a thiourea processing plant in a Russian study in which details as to exposure were not provided. A decrease in T3 levels (<60 ng/100 ml) at normal levels of T4 and a decrease in the leukocyte count were interpreted by the authors to be indicative of thiourea intoxication (Talakin et al., 1990).

Cases of contact dermatitis have been described in thiourea production workers; the contact dermatitis disappeared rapidly after the workers had been transferred to another workplace (Speranski et al., 1969).

Reports of individual cases of contact dermatitis related to the use or processing of thiourea and thiourea compounds have been reviewed (Dooms-Goossens et al., 1987; Kanerva et al., 1994; McCleskey & Swerlick, 2001). Most cases have been reported from the use of thiourea as an antioxidant in diazo copy paper (light-sensitive photocopy paper) and almost all other types of copy paper (Van der Leun et al., 1977; Nurse, 1980; Kellett et al., 1984; Liden, 1984; Dooms-Goossens et al., 1987; Niinim?ki, 1989; Pasche-Koo & Grosshans, 1991; Torres et al., 1992; Geier & Fuchs, 1993; Bartels & Schauder, 1994; van Gerwen et al., 1996; Kanerva et al., 2000). Some cases showed increased sensitivity to UV light (photocontact dermatitis). Contact dermatitis from thiourea in silver polish has also been reported (Dooms-Goossens et al., 1988). Thiourea derivatives such as dimethyl, diethyl, dibutyl, diphenyl, ethylbutyl, and ethylene thiourea are used as accelerators in the vulcanization process in the rubber industry. Products such as wet suits, swimming goggles, orthopaedic devices, protective gloves, and shoes containing these compounds have been shown to produce allergic contact dermatitis (Kanerva et al., 1994; McCleskey & Swerlick, 2001).

It was reported that thiourea compound allergy is relatively rare. An allergic patch test reaction was provoked in only 5 patients out of 423 (1.2%) (Kanerva et al., 1994). Relative to the number of persons exposed to thiourea, the number of reported contact and photocontact allergies to thiourea is small (MAK, 1997).

Thiourea had a former use in the treatment of excessive thyroid gland activity. The doses of thiourea recommended vary considerably. Originally, a dose of 2–3 g daily was used, especially as an initial dose. This was later reduced because of the associated side-effects. The side-effects of thiourea have been described from observations of the former therapeutic use of thiourea in the 1940s as a thyroid depressant (MAK, 1988). Forty-nine (i.e., 9.3%) of 525 patients who were treated with thiourea suffered from one or more of the following side-effects as specified by the respective number of individual cases quoted in parentheses: agranulocytosis (1), leukopenia (4), elevated temperature (24), erythema (9), swollen lymph nodes (1), pains in muscles and joints (4), gastrointestinal disorders (17), and various other symptoms (Vanderlaan & Storrie, 1955). Elevated temperature was observed almost immediately after commencement of the therapy and regressed upon its termination. Both attacks of feverishness, which occur within 7–14 days after the onset of the therapy, and skin reactions have been attributed to sensitization (Peters et al., 1949).

In an early study with hyperthyroid patients (n = 12), it was shown that a dose of 15 mg (about 0.2 mg/kg body weight per day for a 70-kg person) daily for 10–12 weeks was insufficient to depress thyroid activity, as judged by the concentrations of serum precipitable iodine, while a dose of 70 mg daily (1.0 mg/kg body weight per day) in conjunction with iodine solution produced a remission in hyperthyroidism (Winkler et al., 1947).

Four cases of hypothyroidism occurred over a period of 6 years among 539 employees at a textile factory where thiourea and resorcinol were used in the dyeing and finishing processes. A typical level of thiourea at the inlet of the local exhaust ventilation of the stenters was 5 μg/m3, and resorcinol levels were less than 20 μg/m3. The prevalence of hypothyroidism among men appeared to be higher than the rate of <1/1000 found for men in a large epidemiological survey of the adult population in the mixed urban and rural area of Wickham, near Newcastle-upon-Tyne, United Kingdom. The prevalence for women was less remarkable when compared with the rate of 19/1000 found for women in the same survey. The authors concluded that since the employees were exposed to thiourea and resorcinol, both compounds with antithyroid properties, the occurrence of hypothyroidism in this working population could have been work-related (Roberts et al., 1990).

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