[Silica exposure index in gold mining].
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.
Carneiro
Ana Paula Scalia
AP
Ambulatório de Doenças Profissionais, Hospital das Clínicas, Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brazil. apscalia@email.com
Barreto
Sandhi Maria
SM
Siqueira
Arminda Lucia
AL
La Rocca
Poliana Freitas
PF
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001938:Brazil; D003430:Cross-Sectional Studies; D018450:Disease Progression; D004305:Dose-Response Relationship, Drug; D006046:Gold; D006801:Humans; D008297:Male; D008875:Middle Aged; D008906:Mining; D016273:Occupational Exposure / Q000009:adverse effects / Q000032:analysis* / Q000706:statistics & numerical data; D018570:Risk Assessment; D012822:Silicon Dioxide / Q000009:adverse effects / Q000032:analysis*; D012829:Silicosis / Q000175:diagnosis* / Q000209:etiology; D013997:Time Factors
D006046:Gold; D012822:Silicon Dioxide