D Lowson

Work related symptoms, sensitisation, and estimated exposure in workers not previously exposed to laboratory rats

Findings are presented from the initial cross sectional phase of a cohort study of employees exposed to laboratory rats. Of 366 eligible workers at four sites 323 (88%) were surveyed; symptoms assessed by self completed questionnaire and sensitisation measured by the response to skin prick tests were related to intensity of exposure both to total dust and to rat urinary aeroallergen. Among 238 workers, without previous occupational exposure to rats, work related symptoms, which started after first employment at the site were related to exposure intensity (expressed either in terms of dust or of aeroallergen) at the time of onset of symptoms. These relations were stronger in atopic subjects but were unrelated to smoking. Positive skin tests to rat urinary extract were also more frequent with increased exposure, a relation found in both atopic subjects and in smokers. There was a strong association between work related symptoms and specific sensitisation.

Work related symptoms, sensitisation, and estimated exposure in workers not previously exposed to flour

Findings are presented from the initial cross sectional phase of a cohort study of employees exposed to flour in bakeries or mills. Of 401 eligible workers in seven sites 344 (86%) were surveyed; symptoms assessed by self completed questionnaire, and sensitisation measured by the response to skin prick tests, were related to intensity of exposure both to total dust and to flour aeroallergen. Among 264 subjects without previous occupational exposure to flour, work related symptoms which started after first employment at the site were related to exposure intensity, especially when exposure was expressed in terms of flour aeroallergen. The relations with eye/nose and skin symptoms were independent of atopic status and cigarette smoking. Positive skin test responses to mixed flour and to alpha amylase were also more frequent with increasing exposure intensity, although this was confounded by atopic status. There was only a weak association between symptoms and specific sensitisation.

Reduction of airborne allergenic urinary proteins from laboratory rats.

Allergy and asthma caused by proteins of laboratory animals, particularly rats and mice, are the most important occupational health hazards for the scientists and technicians who work with such animals. The influence of different cage litters, cage design, and stock density on measured rat urinary aeroallergen (RUA) concentrations has been examined in a room housing male rats, to determine practical means to reduce allergen concentration in animal laboratories. Eight hour static air samples were taken at 2 1/min and the RUA concentrations measured by radioallergosorbent test (RAST) inhibition. High RUA concentrations occurred when the animals were housed on wood based, contact litter (geometric mean (GM) sawdust 7.79 micrograms/m3; woodchip 6.16 micrograms/m3). The use of noncontact absorbent pads was associated with a significant decrease in RUA concentrations (GM 2.47 micrograms/m3; p less than 0.0001). Rat urinary aeroallergen concentrations fell more than fourfold when the animals were housed on woodbased, contact litter in filter top cages rather than conventional open top cages (GM filter top 0.33 micrograms/m3; open top 1.43 micrograms/m3; p less than 0.0001). The number of rats (stock density) strongly influenced the RUA concentration and a linear relation was found between the log(e) allergen concentration and stock density under these study conditions. The measurement of airborne particle size on cleaning out days showed that all litter types generated similar sized particles: more than 80% of the RUA was carried on particles larger than 8 microns in diameter for all litter types. The findings suggest that the exposure of animal husbandry personnel to RUA may be substantially reduced by the avoidance of contact litter, the use of filter top cages (where suitable), and by keeping stock density to a minimum.

Dust and flour aeroallergen exposure in flour mills and bakeries.

As part of an epidemiological study among workers exposed to flour total dust and flour aeroallergen concentrations were measured with personal samplers over a workshift in three large bakeries and four flour mills and packing stations. In the bakeries geometric means for total dust concentrations ranged from 0.4 mg/m3 in the bread wrapping area up to 6.4 mg/m3 at the dough brake. The flour aeroallergen concentrations ranged from 45.5 micrograms/m3 in the bread wrapping area up to 252.0 micrograms/m3 in the confectionary area. In the flour mills and packing stations the concentrations were higher with geometric means for total dust ranging from 0.5 mg/m3 in the office up to 16.9 mg/m3 for hygiene workers in an old mill. The flour aeroallergen concentrations ranged from 101.5 micrograms/m3 for transport workers up to 1728.2 micrograms/m3 for hygiene workers. The relation between total dust and flour aeroallergen concentrations varied for different areas and depended on the use of products other than flour.

Measurement of airborne rat urinary allergen in an epidemiological study

The suitability of radioallergosorbent test (RAST) inhibition to quantify occupational exposure to rat urinary aeroallergen (RUA) has been assessed. When using a constant pool of rat allergic sera, the reproducibility of the assay over 1 year was comparable to that reported for other immunoassays; at 50% RAST inhibition the inter‐assay coefficient of variation (CV) was 7.0% and the intra‐assay CV was 3.0%. The assay was highly specific for rat urine; mouse urine was 1100‐fold less potent at inhibiting the rat urine RAST system. Significant inter‐assay variation in the ‘high’ control was not due to batch variation and was relatively small when compared with the variation in RUA concentrations in the occupational environment. Measurement of workplace RUA exposure demonstrated that those directly involved in the care of rats experienced the highest RUA exposure of the nine occupational groups studied (animal technicians GM = 23.10/μg/m3) followed in decreasing order by those working with soiled litter (e.g. cage cleaners GM = 4.20 μg/m3), dead animals (e.g. post mortem GM = 1.60 μg/m3, scientists GM = 0.67 μg/m3) and rat tissue (e.g. slide production GM = 0.04μg/m3). In view of the complexity of rat allergens, RAST inhibition is an appropriate method for the quantification of occupational exposure to rats.

PEAK EXPOSURE CONCENTRATIONS OF DUST AND FLOUR AEROALLERGEN IN FLOUR MILLS AND BAKERIES

As part of an epidemiological study amongst workers exposed to flour we measured peak exposure levels to total dust and flour aeroallergen with personal samplers in bakeries, flour mills and packing stations. Short-term tasks which were expected to give rise to high concentrations of exposure (peaks) were identified. The frequency and duration of these tasks were estimated and their levels of exposure to dust and flour aeroallergen measured. In total 209 samples were taken. The highest exposure concentrations both for dust (geometric mean > 30 mg m-3) and for flour aeroallergen (geometric mean > 500 micrograms m-3) were measured during certain operations. Exposure concentrations for the tasks were often much higher than the levels we had measured over a shift in a previous study. This might be important for sensitization and for the development of asthma. Peak exposure concentrations could be used to explore the exposure-response relationship more comprehensively. In general average flour aeroallergen concentrations increased linearly with average dust concentrations, although there were some exceptions.

Flour dust exposure variability in flour mills and bakeries

As part of a longitudinal study to explore the exposure-response relationship between flour dust exposure and work-related symptoms and skin sensitivity the authors formed exposure groups and estimated various components of variability. This paper describes the between-exposure group, the between-worker and the within-worker variation of personal flour dust exposure in bakeries, flour mills and packing stations. In total 346 samples were collected in 13 exposure groups. The geometric means of the exposure groups ranged from 0.3 up to 9.0 mg m-3. Between-worker variances within exposure groupings were less than the overall between-worker component although substantial differences in exposure between workers remained in some exposure groups. Overall the largest variance component was the between-exposure group component followed by the considerably smaller between-worker and within-worker components.