Stone crushing in Dar-es-Salaam Tanzania is largely an informal occupational activity,
with approximately 7000 workers exposed to varying level of respirable dust. A highly
marginalized, self employed, informal stonecrusher is prone to multiple work related risks,
particularly dust related respiratory diseases.
This study, the first to be done among informal stone crushers in Southern Africa,
aimed at determining the prevalence of dust related respiratory outcomes and relationships
between these health endpoints and exposure to respirable dust in this sample of stonecrushers.
This was primarly a cross-sectional descriptive study with analytic components. This
study analysed a subset of data collected in a health survey of stone crushers in Kigamboni
informal stone quarry in Dar-es-Salaam, Tanzania in 2007. All 200 workers working in the
quarry were interviewed. A subset of 86 and 59 workers underwent exposure assessment and
health assessments (spirometry and chest radiography) respectively. Associations were
investigated between exposure measures and respiratory outcomes.
The average age of the workers was 36.3 years with 51.5% males participating in the
study. Smoking was common with 30.1% male, 8.25% female smokers, with 2% ex-smokers.
Personal dust sampling showed varying dust levels ranging from 0.5-2.8mg/m3 with geometric
mean of 1.2gm/m3. The exposure duration of workers in the quarry ranged from 1-62 years
with mean of 7.8 years. No single worker was found to use personal protective equipment at
Reported prevalence of doctor diagnosed respiratory diseases was low: pulmonary
tuberculosis (2%), chronic bronchitis (2%), asthma (3%), pneumonia (3%). In contrast, there
was high prevalence of respiratory symptoms: chronic cough (13.5%), phlegm production
(14.5%), productive cough (10%), wheezing (14%), mild breathlessness (9.5% ) and coughing
blood (7.5%). Mean forced expiratory volume in one second (FEV1) and forced vital
capacity (FVC) adjusted for age, height and sex was 2.6L/min and 3.7 L respectively, among
males and 2.1L/min and 3.0L respectively among females.
Adjusted exposure odds ratios for symptoms were statistically significant for mild and
moderate breathlessness with odds ratios of 3.4 and 3.1 respectively.
Linear regression showed statistically significant decline of 2.3mls in FEV1 with years
of exposure while controlling for sex, age, height , doctor diagnosed TB and smoking showing
that with prolonged exposure in the quarry, workers are at a risk of developing obstructive lung
disease. This trend was not evident for FVC.
The majority of films were normal (60.9%), with 19.6% read as 1/0 and 19.9% as 0/1.
This study identified adverse respiratory outcomes among informal stonecrushers,
particularly a high prevalence of respiratory symptoms and clinically important lung function
deficits. These are in keeping with other environment studies where workers were exposed to
Urgent policy initiatives for developing cost effective hazard control, engineering
interventions to protect these marginalized self-employed informal sector stonecrushers are