Health Effects of Exposure to Flour Dust and Microbial Contaminants in Egyptian Mills
Mahmoud S. El-Bukhary1, Hala I. Awadalla2, Adel Khattab2, and Khaled Ezz El-Din3
1 Institute of Environmental Studies and Research, Egypt
2 Faculty of Medicine, Ain Shams University, Ain Shams University, Egypt
3 Embaba Chest Hospital, Egypt
Corresponding author: Hala I. Awadalla
Faculty of Medicine, Ain Shams University, Ain Shams University
Cairo, Egypt
E-mail: Hala_awadalla@yahoo.com
CEJOEM 2007, Vol.13. No.2.: 179–191
Key words:
Flour-dust; bacteria; hazards; moulds; asthma; lung function
Abstract:
Background: Flour dust is a heterogeneous substance with respiratory sensitizing properties, its long-term
exposure may cause acute or chronic respiratory diseases.
Subjects and Methods: Two flour mills were randomly selected from Greater Cairo, Egypt. Sixty exposed male
workers (occupationally exposed), sixty exposed males living nearby the mills (environmentally exposed) and one
hundred unexposed controls were included in the study. Samples were taken from both mills, the external environment
and from control areas to determine the concentrations of inhalable flour dust. Air samples for microbiological analysis
were also taken. All subjects completed a questionnaire on respiratory symptoms, Pulmonary function tests and skin testing
were done to study population.
Results: Aerial microbial contamination differed greatly in the various areas of the mills; the mean values of
contamination by total bacteria were significantly different at the points analyzed. Mean concentrations in filling area
(41.11 CFU/m3) were higher than other units and the nearby external environment. The highest concentration
of moulds was found in the filling and bran–collecting areas. Mean flour dust concentrations above 10 mg/m3
were observed in all units of the mills and the highest concentrations were found in filling areas
(19.27 mg/m3). The prevalence of asthma and wheezing in environmentally exposed persons to flour dust was
higher than controls (p<0.05), while in the occupationally exposed workers, there was a statistically significant greater
prevalence of chronic cough or phlegm, asthma, wheezing, and running nose compared to the control group (p<0.05).
FVC%, FEV1%, FEV1/FVC% values were significantly decreased in flour exposed subjects (occupationally or environmentally)
compared to the control subjects (p<0.001). A positive skin test to wheat flour antigen was reported in 30% of
environmentally exposed subjects, in 58.3% of flour exposed workers and in 4% of control subjects, and this difference
was highly significant (p<0.001). Subjects with skin test positive to flour antigen were found to have significantly
lower values of baseline pulmonary function parameters than subjects with negative skin test to flour antigen.
Conclusions: (1) Subjects exposed to flour dust are at greater risk of developing respiratory symptoms, asthma and
chronic bronchitis. (2) Flour dust causes an obstructive pattern of lung function impairment.
Recommendations: (1) Assessment of air quality through regular checking of microbiological pollutants of flour dust
is mandatory in order to establish air quality standards. (2) Use of technical measures to reduce microbiological burden in
flour mills is highly stressed to prevent consequent adverse health effects.
Received: 11 April 2007
Accepted: 23 November 2007
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