Is Occupational Asthma in Dentists Associated with Exposure to DUWL?

Objectives: The majority of organisms isolated from dental waterlines (DUWL) are Gram-negative bacteria, which contain cell wall endotoxin. Exposure to endotoxin is associated with the exacerbation of asthma. In this preliminary study we examined whether the prevalence and onset of asthma in dentists recruited in a cross-sectional study evaluating contaminated DUWL was associated with the microbiological quality of the water. Methods: 266 Dentists (100 rural Ulster, 166 London) were randomly selected from Health Authorities’ registers. A health questionnaire including questions on prevalence and time of onset of asthma was completed. 250 ml overnight water was sampled from the dental hand pieces and 1L of water was sampled from the surgery washbasin cold tap. Microbial water analysis was conducted using standard techniques. Questionnaire data was evaluated using multivariable analysis of variance by correlation with the following: - smoking; surgery location; time treating patients per week; DUWL counts of Pseudomonas aeruginosa, total Pseudomonas spp, fungi, Mycobacterium spp, total aerobic bacterial counts at 220 C and 370 C. Results: Among dentists reporting, “ever having asthma” there was no significant correlation with the variables tested. A subgroup analysis was performed on dentists (n = 33) who developed asthma “since they started training as a dentist”. The final multivariable model indicated that passive smoking (OR 0.08, 95% CI 0,01 0.87, p=0.038) and total aerobic counts at 370C >200 cfu/ml (OR 6.72, 95% CI 1.15-39.24, p= 0.034) were significant variables for developing asthma since starting training as a dentist. London Dentists were more likely to have developed asthma since starting training than their Ulster counterparts (London: OR 4.4, 95% CI 1.09-17.72, p= 0.033). Total aerobic counts were significantly higher in London (p<0.0001). Conclusions: This preliminary study suggests that temporal onset of asthma may be associated with occupational exposure to contaminated DUWL. Grant: NHS RDO/90/08