Índice de exposição à sílica na atividade de mineração de ouro Silica exposure index in gold mining

Abstract

OBJETIVO: Propor um índice que sintetize a exposição cumulativa à sílica, incluindo intensidade, duração e época da exposição e testá-lo em relação à presença e gravidade de silicose. MÉTODOS: Estudo transversal realizado com 140 ex-mineiros de ouro, residentes em duas localidades do Estado de Minas Gerais, examinados entre 11/1997 e 12/1999. Foram analisadas informações sobre história clínica e ocupacional, radiografia de tórax e espirometria. Casos borderline de silicose pela radiografia foram submetidos à tomografia computadorizada de alta resolução. O índice representa a soma dos escores extraídos da transformação logarítmica das taxas de concentração de sílica respirável nas diversas funções, minas e períodos trabalhados. Foram aplicados testes paramétricos para comparação das médias entre os grupos de interesse. RESULTADOS: O índice proposto apresentou-se discriminativo em relação ao desfecho principal (silicose) e aos desfechos secundários (enfisema e tuberculose) pulmonar no grupo total, incluindo os diversos estágios da doença, com valores p: 0,008, 0,016 e OBJECTIVE: To develop a cumulative silica exposure index, including time period, duration and intensity of exposure, and to test this index as for occurrence and severity of silicosis. METHODS: A cross-sectional study was carried out comprising 140 former gold miners from two localities in Southeastern Brazil between November 1997 and December 1999. Complete data on occupational and medical histories, chest x-rays and spirometry were analyzed. Borderline cases on the x-rays were also submitted to high-resolution chest computed tomography. The exposure index was the sum of scores obtained by logarithmic transformation of respirable silica concentration related to job tasks, mines and work time. Parametric tests were used for comparing averages between the groups of interest. RESULTS: The silica exposure index was able to discriminate the main outcome (silicosis) as well as other outcomes (tuberculosis and lung emphysema) in the whole group at p-values of 0.008, 0.016 and <0.001 respectively. In regard to the four main categories of silicosis, the Tukey test showed differences in the averages of the exposure index in the categories 0 and 3 and 1 and 3. However, in the borderline cases subgroup, the exposure index was not satisfactory for cases submitted to x-rays and tomography and it could not differentiate other outcomes. CONCLUSIONS: The silica exposure index represents an advance in exposure evaluation of former miners. However, other information, such as clinical and lung functional data are needed for better understanding disease progress in silica exposed cases, especially among borderline cases.

Keywords

• Sílica
• Silicose
• Exposição ocupacional
• Indicadores de exposição
• Estudos transversais
• Silicon dioxide
• Silicosis
• Occupational exposure
• Exposure indicators
• Cross-sectional studies