Exposure–response relationships of occupational inhalative allergens

Abstract

Only a few threshold limit values exist at present for allergens in the workplace known to cause bronchial asthma. This contrasts with the great number of occupational asthma cases observed in industrialized countries. Recently published studies provide clear evidence for exposure intensity response relationships of occupational allergens of plant, microbiological, animal or man-made origin. If allergen exposure levels fall short of determined limit values, they are not associated with an increased risk of occupational asthma. Corresponding data are available for wheat flour (1-2.4 mg/m3), fungal alpha-amylase (0.25 ng/m3), natural rubber latex (0.6 ng/m3), western red cedar (0.4 mg/m3) and rat allergens (0.7 microg/m3). It is suggested to stipulate legally binding threshold limit values (TLV/TWA) on this basis in order to induce more effective primary preventive measures. If no reliable data on the health risk of an occupational airborne noxa exist, the lowest reasonably practicable exposure level has to be achieved. Appropriate secondary preventive measures have to be initiated in all workplaces contaminated with airborne allergens. Verified exposure-response relationships provide the basis for risk assessment and for targeted interventions to reduce the incidence of occupational asthma also in consideration of cost benefit aspects. 'Occupational asthma is a disease characterized by variable airflow limitation and/or airway hyperresponsiveness due to causes in a working environment. These causes can give rise to asthma through immunological or non-immunological mechanisms. Up to 15% of all asthma cases are of occupational origin or have at least a significant causal occupational factor. According to the New Zealand part of the European Respiratory Health Survey, an increased risk of asthma prevalence was found for several occupations such as laboratory technicians, food producers, chemical workers, plastic and rubber workers. The Spain part of this study comprising 2646 Spanish subjects showed an asthma risk to be attributed to occupational exposures between 5 and 6.7%. Main asthma-inducing agents in the workplace are flour, grain and feed dust, animal dander/urinary proteins and isocyanates. Further, several inhalative irritants such as chlorine, acid or alkaline aerosols play a pivotal role. Many low molecular weight chemicals have irritative as well as allergenic effects on the airways, e. g. isocyanates and acid anhydrides. In addition to chronic or repetitive exposures, also singular accidental exposure to high concentrations of irritative or toxic airborne substances can cause occupational asthma. This condition is frequently called reactive airways dysfunction.

Beryllium: A Modern Industrial Hazard

“…Evidence that sensitization is exposure related exists for many substances, for example isocyanates and enzymes (1). Once sensitized, workers can react to much lower levels of exposure, sometimes below limits of detection.…”

Controversies in epidemiology of occupational asthma

“…Studies such as these are costly and time consuming, but they provide evidence of sufficient strength to enable the development of preventive strategies for the most significant causes of OA, including flour, for which acceptable limits of exposure to prevent sensitisation and disease have been proposed [78]. Similar thresholds need to be proposed for other occupational agents [79].…”

Levels of soya aeroallergens during dockside unloading as measured by personal and static sampling / Razine aeroalergena soje za vrijeme iskrcavanja na lučkom doku

“…However, studies on other occupational allergens have reported that averting or decreasing allergen exposure in the workplace is the most effective approach for preventing asthma (27). Thus, this current lack of data does not obviate the uses of either the HSP and STI assays as a means of monitoring the effectiveness of workplace control measures in reducing exposure to inhalable soya allergens to as low as is reasonably practical.…”