Effect of Occupational Exposure to Silica Dust on the Thyroid Gland in Ceramic Workers

Safia Beshir Ahmed, Hesham Mohamed Aziz, and Safaa Mohamed Elserougy

Department of Environmental and Occupational Medicine, National Research Center, Cairo, Egypt

Corresponding author: Safaa Mohamed Elserougy
    Department of Environmental and Occupational Medicine
    National Research Centre, Cairo, Egypt
    Fax number: 00202-3370931
    E-mail: safaaser@yahoo.com

CEJOEM 2007, Vol.13. No.1.: 33–42


Key words:
Silica dust, thyroid hormones, occupational exposure, autoimmune antibodies, ceramic industry


Abstract:
In the present study, occupational exposure to crystalline silica dust has been examined as a possible risk factor with respect to thyroiditis as an autoimmune disease. Sixty one exposed workers from a ceramic factory versus 68 controls of same age, socioeconomic status and habits were included. Data were collected through a questionnaire and clinical examination. Biochemical analyses of serum thyroid stimulating hormone (TSH), thyroid hormones [total tri-iodothyronine (T3), Free tri-iodothyronine (FT3), total thyroxine (T4) and Free thyroxine (FT4), serum angiotensin-converting enzyme (ACE) and some auto-antibodies (serum anti-thyroid antibodies (ATHA), anti-nuclear antibodies (ANA), anti-smooth muscle antibodies (ASMA), anti-parietal cell antibodies (APCA), anti-mitochondrial antibodies (AMA), and liver kidney microsomal antibodies (LKM) were done.
    Results: Enlarged thyroid gland was found in only two workers (exposed for more than 10 yrs.). Statistical analysis showed that the means of serum T3, FT3 and FT4 were significantly higher in the exposed workers than in the controls, while the mean of T4 was significantly lower. The frequency of ATHA was significantly higher in the exposed than in the control group (p<0.05) while other auto-antibodies showed statistically non-significant difference. A highly significant positive correlation was found between the duration of exposure to silica dust and the thyroid hormone serum levels. The present study concluded that occupational silica dust exposure may affect the activity of thyroid gland hormones even in the absence of clinical features, through an autoimmune mechanism and detection of anti-thyroid antibody (ATHA) levels in workers exposed to silica dust can be of great value as a biomarker or a predictor factor for early thyroid gland dysfunction.


Received: 23 March 2007
Accepted: 08 June 2007

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