Prevalence of Chronic Autoimmune Thyroiditis in the Urban Area Neighboring a Petrochemical Complex and a Control Area in Sao Paulo, Brazil

Abstract

PURPOSE: To evaluate the prevalence of chronic autoimmune thyroiditis in 2 urban areas of metropolitan São Paulo (Brazil): Polo Area neighboring a large petrochemical complex and São Bernardo Campo Area (control area). SUBJECTS AND METHODS: Subjects were randomly included from the adult population (20 to 70 years of age) of both genders (women 80%, men 20%) who voluntarily agreed to participate. From the Polo Area, in the vicinity of a large petrochemical industrial complex, 409 subjects were included; from the control area (São Bernardo Campo Area) 420 individuals were included. All subjects were clinically examined, and a detailed record of past thyroid illness and medications was obtained. Ultrasonographic studies were performed using a portable GE Medical Systems apparatus. Blood samples were obtained for free T4, serum TSH, and serum anti-thyroid peroxidase autoantibodies. Urine specimens were collected in Monovette syringes for assaying iodine content. Salt samples were collected at households, and the iodine content was measured. RESULTS: Chronic autoimmune thyroiditis was diagnosed both echographically (marked hypoechogenicity) and immunologically (presence of autoantibodies against thyroid peroxidase). In the Polo Area, 15.6% of the examined population had chronic autoimmune thyroiditis, and in the control area (São Bernardo Campo Area), 19.5% of the population had evidence of chronic autoimmune thyroiditis (P > 0.057, not significant). The prevalence of hypothyroidism was 4.9% in the Polo Area and 8.3% in the São Bernardo Campo Area (P = 0.0461 significant). Taking the 2 populations together, 6.6% had hypothyroidism (about one third of these patients were on L-T4 treatment). The mean thyroid volume was 11.2 mL. Domestic salt had a normal concentration of iodine (35.5 + 6.61 mg/kg). Urinary excretion of iodine was above 300 μg Iodine/L in 58.5% of the total population. CONCLUSION: The high iodine intake (above 300 μg Iodine/L of urine) that was present from 1998 through 2005 may be related to a higher prevalence of chronic autoimmune thyroiditis in both areas that were studied. There was no apparent or documented relationship of chronic autoimmune thyroiditis prevalence to the proximity to the petrochemical complex.

Chronic lymphocytic thyroiditis: could it be influenced by a petrochemical complex? Data from a cytological study in South-Eastern Sicily

“…Two Brazilian groups (12,13) have addressed the association of HT with the petrochemical complex-related pollution by targeting the same area surrounding the petrochemical complex of Capuava (municipality of Santo André, State of Sao Paulo), but two different control areas, though both control areas were located at similar distance (about 16 km away from the complex). Results differed because the rate of the endocrine diagnosis of HT was similar to that of the control area (15.6% vs 19.5%) in one study (12) and it was twofold greater (9.3% vs 3.9%) in the other study (13).…”

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