Wijnand Eduard

Do farming exposures cause or prevent asthma? Results from a study of adult Norwegian farmers

Background: A protective effect of endotoxin exposure on atopy and asthma in farmers’ children has been postulated. Studies of adult farmers have shown conflicting results but often lack exposure data. The prevalence of asthma in farmers with different exposure levels to microbial agents and irritant gases was compared. Methods: Atopy was defined as a positive response to multiple radioallergosorbent tests (RAST) with a panel of 10 common respiratory allergens, and asthma was ascertained by a questionnaire using a stratified sample (n = 2169) of a farming population from south-eastern Norway. Exposure of farmers to total dust, fungal spores, bacteria, endotoxins, and ammonia was assessed by exposure measurements. Results: The prevalence of asthma was 3.7% for physician diagnosed asthma and 2.7% for current asthma. The prevalence of atopy was 14%, but most asthmatic subjects were non-atopic (80%). Compared with farmers without livestock, (1) asthma was significantly higher in cattle farmers (ORadj 1.8, 95% CI 1.1 to 2.8) and pig farmers (ORadj 1.6, 95% CI 1.0 to 2.5), (2) non-atopic asthma was significantly higher in pig farmers (ORadj 2.0, 95% CI 1.2 to 3.3) and in farmers with two or more types of livestock (ORadj 1.9, 95% CI 1.1 to 3.3), and (3) atopic asthma was less common in farmers with two or more types of livestock (ORadj 0.32, 95% CI 0.11 to 0.97). Exposure to endotoxins, fungal spores, and ammonia was positively associated with non-atopic asthma and negatively associated with atopic asthma. No associations were found with atopy. Conclusions: Exposure to endotoxins and fungal spores appears to have a protective effect on atopic asthma but may induce non-atopic asthma in farmers.

Chronic Bronchitis, COPD, and Lung Function in Farmers: The Role of Biological Agents

BACKGROUND Farmers have an increased risk of respiratory morbidity and mortality. The causal agents have not been fully established. METHODS In a cross-sectional study of 4,735 Norwegian farmers, we assessed respiratory symptoms and lung function. Atopy was assessed in a subsample (n = 1,213). Personal exposures to dust, fungal spores, actinomycete spores, endotoxins, bacteria, storage mites, (1-->3)-ss-D-glucans, fungal antigens, organic dust, inorganic dust, silica, ammonia, and hydrogen sulfide were measured for 127 randomly selected farms. RESULTS Compared to crop farmers, livestock farmers were more likely to have chronic bronchitis (odds ratio [OR], 1.9; 95% confidence interval [CI], 1.4 to 2.6) and COPD (OR, 1.4; 95% CI, 1.1 to 1.7). FEV(1) (-41 mL; 95% CI, -75 to -7) was significantly reduced, but FVC (-15 mL; 95% CI, -54 to 24) was not. Exposure to most agents were predictors of respiratory morbidity, except FVC. Ammonia, hydrogen sulfide, and inorganic dust were most strongly associated in multiple regression models adjusted for coexposures, but the effects of specific biological agents could not be assessed in multiple regression models because they were too highly correlated. Farmers with atopy had a significantly lower FEV(1) (OR, -87 mL; 95% CI, -170 to -7), but atopy was not directly associated with chronic bronchitis, COPD, and FVC. However, the effects of farming and specific exposures on COPD were substantially greater in farmers with atopy. CONCLUSIONS Livestock farmers have an increased risk of chronic bronchitis, COPD, and reduced FEV(1). Ammonia, hydrogen sulfide, inorganic dust, and organic dust may be causally involved, but a role for specific biological agents cannot be excluded. Farmers with atopy appear more susceptible to develop farming-related COPD.

Fungal spores: A critical review of the toxicological and epidemiological evidence as a basis for occupational exposure limit setting

Fungal spores are ubiquitous in the environment. However, exposure levels in workplaces where mouldy materials are handled are much higher than in common indoor and outdoor environments. Spores of all tested species induced inflammation in experimental studies. The response to mycotoxin-producing and pathogenic species was much stronger. In animal studies, nonallergic responses dominated after a single dose. Allergic responses also occurred, especially to mycotoxin-producing and pathogenic species, and after repeated exposures. Inhalation of a single spore dose by subjects with sick building syndrome indicated no observed effect levels of 4 × 103 Trichoderma harzianum spores/m3 and 8 × 103 Penicillium chrysogenum spores/m3 for lung function, respiratory symptoms, and inflammatory cells in the blood. In asthmatic patients allergic to Penicillium sp. or Alternaria alternata, lowest observed effect levels (LOELs) for reduced airway conductance were 1 × 104 and 2 × 104 spores/m3, respectively. In epidemiological studies of highly exposed working populations lung function decline, respiratory symptoms and airway inflammation began to appear at exposure levels of 105 spores/m3. Thus, human challenge and epidemiological studies support fairly consistent LOELs of approximately 105 spores/m3 for diverse fungal species in nonsensitised populations. Mycotoxin-producing and pathogenic species have to be detected specifically, however, because of their higher toxicity.

Methods for Quantitative Assessment of Airborne Levels of Noninfectious Microorganisms in Highly Contaminated Work Environments

Exposure to high airborne levels of noninfectious microorganisms is recognized as a cause of respiratory symptoms and disease among workers handling biological materials, such as farmers, sawmill workers, and workers handling municipal waste and fuel chips. Risk assessment is difficult because occupational exposure limits for noninfectious microorganisms have not been established. Many different methods are used for the measurement of airborne microorganisms, which are based on impaction, impingement, or filtration. Samples can be analyzed by methods that are culture-based or nonculture-based and that may estimate different microbial entities: culturable microorganisms by culture-based methods, microbial cells by microscopic methods, and microbial constituents and products by chemical, biochemical and immunochemical methods. Sources of errors and validation studies of these methods are reviewed and methods are evaluated for exposure assessment in epidemiological studies and for future compliance testing. At present it is not clear which microbial bioaerosol components should be assessed. Culture-based methods are probably not satisfactory because nonviable microorganisms and microbial constituents and products also may cause health effects. Culture-based methods are poor surrogates for nonculture-based methods and have poor precision. However, identification of microorganisms is most readily performed by culture-based methods. Filter sampling is preferred for personal exposure measurements because filters can be analyzed by a variety of nonculture-based methods, and filter sampling may be adapted to recently adopted criteria for health-related size fractions.

Short term exposure to airborne microbial agents during farm work: exposure-response relations with eye and respiratory symptoms

OBJECTIVES Exposure to high levels of non-infectious microbial agents is recognised as a cause of respiratory disease in working populations, but except for endotoxins, little is known about exposure-response relations. As these effects do not depend on viability, exposure to non-viable microbial agents is important. Various methods not based on microbial cultures were explored to study the complex microbial exposure of farmers and associations with acute symptoms during work. METHODS Airborne exposure was measured when farmers carried out specific tasks. Fungal spores, bacteria, endotoxins, β(1→3)-glucans, fungal antigens specific for Penicillium andAspergillus species, and mites were measured by methods not based on microbial cultures. Also silica, inorganic and organic dust, ammonia, hydrogen sulphide, and nitrogen dioxide were measured. Respiratory, and nose and eye symptoms experienced during measurements were recorded by a short questionnaire. Both univariate and multivariate statistical analyses were applied to assess the relations between exposure and acute symptoms. RESULTS 106 Farmers and their spouses participated in this study. Prevalences of work related symptoms were: wheezing 3%; chest tightness 7%; cough 14%; eye symptoms 18%; and nose symptoms 22%. Prevalence ratios for nose and eye symptoms were 4–8 after exposure to 20–500×103fungal spores/m3 and higher, and a prevalence ratio for cough was 4 after exposure to 500–17 000×103 fungal spores/m3. Nose symptoms were also associated with exposure to silica with prevalence ratios of 4–6 after exposure to 0.015–0.075 mg /m3 and higher. CONCLUSIONS Farmers had a high occurrence of symptoms of the nose and eyes as well as cough during work. These symptoms were associated in a dose dependent manner with exposure to fungal spores. Nose symptoms were also associated with exposure to silica.

Upper airway inflammation in waste handlers exposed to bioaerosols

Aims: To examine work associated upper airway inflammation in 31 waste handlers, and to correlate these findings with personally monitored exposure to different bioaerosol components. Methods: Cell differentials, interleukin 8 (IL-8), myeloperoxidase (MPO), and eosinophilic cationic protein (ECP) were examined in NAL (nasal lavage), and swelling of the nasal mucosa was determined by acoustic rhinometry before work start on Monday and the following Thursday. Bioaerosol exposure was determined by personal full shift exposure measurements on Monday, Tuesday, and Wednesday and analysed for total bacteria, fungal spores, endotoxin, and β(1→3)-glucans. Results: The increased percentage of neutrophils from Monday (28%) to Thursday (46%) correlated with increases in ECP (rS = 0.71, p < 0.001) and MPO (rS = 0.38, p < 0.05), and showed a close to significant correlation with nasal swelling (rS = −0.55, p = 0.07). The Thursday levels of neutrophils, MPO, and IL-8 were associated with the exposure to fungal spores (range 0–2.0 × 106/m3) and endotoxin (range 4–183 EU/m3) measured the day before, and the median exposure to β(1→3)-glucans (range 3–217 ng/m3), respectively (rS = 0.47–0.54, p < 0.01). Swelling of the nasal mucosa was associated with the fungal spore and β(1→3)-glucan exposure (rS = 0.58–0.59, p < 0.05). Conclusion: These results are based on a relatively small population, and conclusions must be drawn with care. The results suggested that a moderate exposure to fungal spores, endotoxins, and β(1→3)-glucans during waste handling induced upper airway inflammation dominated by neutrophil infiltration and swelling of the nasal mucosa.

Ochratoxin A in airborne dust and fungal conidia.

Farm workers are often exposed to high concentrations of airborne organic dust and fungal conidia, especially when working with plant materials. The purpose of this investigation was to study the possibility of exposure to the mycotoxin ochratoxin A (OTA) through inhalation of organic dust and conidia. Dust and aerosol samples were collected from three local cowsheds. Aerosol samples for determination of total conidia and dust concentrations were collected by stationary sampling on polycarbonate filters. Total dust was analysed by gravimetry, and conidia were counted using scanning electron microscopy. A method was developed for extraction and determination of OTA in small samples of settled dust. OTA was extracted with a mixture of methanol, chloroform, HCI, and water, purified on immunoaffinity column, and analysed by ion-pair HPLC with fluorescence detection. Recovery of OTA from spiked dust samples (0.9–1.0 μg/kg) was 74% (quantitation limit 0.150 μg/kg). OTA was found in 6 out of 14 settled dust samples (0.2–70 μg/kg). The total concentration of airborne conidia ranged from < 1.1 × 104 to 3.9 × 155 per m3, and the airborne dust concentration ranged from 0.08 to 0.21 mg/m3. Conidia collected from cultures of Penicillium verrucosum and Aspergillus ochraceus contained 0.4–0.7 and 0.02–0.06 pg OTA per conidium, respectively. Testing of conidial extracts from these fungi in a Bacillus subtilis bioassay indicated the presence of toxic compounds in addition to OTA. The results show that airborne dust and fungal conidia can be sources of OTA. Peak exposures to airborne OTA may be significant, e.g., in agricultural environments.

Airway inflammation in waste handlers exposed to bioaerosols assessed by induced sputum

Work-associated lower airway inflammation in waste collectors was examined by induced sputum and correlated with the bioaerosol exposure. Organic waste collectors (n=25) underwent induced sputum collection and spirometry before work on Monday and the following Thursday. Total cells, cell differentials, interleukin (IL)-8 and eosinophilic cationic protein were determined. Personal full-shift exposure measurements were performed Monday, Tuesday and Wednesday and analysed for total bacteria, fungal spores, endotoxins and β(1–3)-glucans. The percentage of neutrophils (46–58%) and the IL-8 concentration (1.1–1.4 ng·mL−1) increased from Monday to Thursday. Forced expiratory volume in one second (FEV1) was significantly reduced on Thursday, and the decrease in FEV1/forced vital capacity correlated with the increase in the percentage of neutrophils. The median exposure to endotoxin (range 7–180 EU·m−3) and β(1–3)-glucan (range 5–220 ng·m−3) was correlated with the increase in IL-8. Bioaerosol exposure during waste collection induced an inflammatory response in the lower airways, characterised by neutrophils and interleukin-8 secretion, that influenced the lung function. The inflammatory response was related to microbial components in the bioaerosol and was more pronounced for endotoxin than β(1–3)-glucan exposure. No associations were found for mould spores or bacteria.

Cumulative exposure to dust causes accelerated decline in lung function in tunnel workers

OBJECTIVES To examine whether underground construction workers exposed to tunnelling pollutants over a follow up period of 8 years have an increased risk of decline in lung function and respiratory symptoms compared with reference subjects working outside the tunnel atmosphere, and relate the findings to job groups and cumulative exposure to dust and gases. METHODS 96 Tunnel workers and a reference group of 249 other heavy construction workers were examined in 1991 and re-examined in 1999. Exposure measurements were carried out to estimate personal cumulative exposure to total dust, respirable dust, α-quartz, oil mist, and nitrogen dioxide. The subjects answered a questionnaire on respiratory symptoms and smoking habits, performed spirometry, and had chest radiographs taken. Radiological signs of silicosis were evaluated (International Labour Organisation (ILO) classification). Atopy was determined by a multiple radioallergosorbent test (RAST). RESULTS The mean exposure to respirable dust and α-quartz in tunnel workers varied from 1.2–3.6 mg/m3 (respirable dust) and 0.019–0.044 mg/m3 (α-quartz) depending on job task performed. Decrease in forced expiratory volume in 1 second (FEV1) was associated with cumulative exposure to respirable dust (p<0.001) and α-quartz (p=0.02). The multiple regression model predicted that in a worker 40 years of age, the annual decrease in FEV1 would be 25 ml in a non-exposed non-smoker, 35 ml in a non-exposed smoker, and 50–63 ml in a non-smoking tunnel worker (depending on job). Compared with the reference group the odds ratio for the occurrence of new respiratory symptoms during the follow up period was increased in the tunnel workers and associated with cumulative exposure to respirable dust. CONCLUSIONS Cumulative exposures to respirable dust and α-quartz are the most important risk factors for airflow limitation in underground heavy construction workers, and cumulative exposure to respirable dust is the most important risk factor for respiratory symptoms. The finding of accelerated decline in lung function in tunnel workers suggests that better control of exposures is needed.

Evaluation of Methods for Enumerating Microorganisms in Filter Samples from Highly Contaminated Occupational Environments

Scanning electron microscopy (SEM), light microscopy (LM), epifluorescence microscopy (FM), and culture were used to assess catches of microorganisms in parallel air samples on membrane filters from heavily contaminated working environments that differed in the relative abundance of bacteria, actinomycetes, and fungal spores. Except in pig houses, estimates by SEM and LM were similar, but those by FM and culture were smaller. However, in pig houses, the fluorescent stain enabled bacteria on skin scales, not seen by SEM or LM, to be counted. Although counts obtained by culturing were always smaller than those obtained by SEM or LM, they sometimes exceeded those obtained by FM. Counts suggested that 0.1-68% of bacteria + actinomycetes and 3-98% of fungal spores were viable. However, samples for culturing may have contained larger aggregates than parallel samples collected within a sampling apparatus. All spore types recognized by LM included aggregates--those of bacteria + actinomycetes sometimes exceeding 200 units, while Wallemia sebi spore aggregates were never larger than 3 spores. The size distributions of all types approximated to log-normal, although single spores and small aggregates of bacteria + actinomycetes were perhaps underrepresented. When spores were counted directly on the filter surface, as by SEM and LM, allowance was necessary for heavier deposition of particles near the center of filters by distributing counting fields systematically over the whole filter or a sector of it. Deposition was more uniform in graphite-filled polypropylene filter holders used open-faced. Losses within filter holders and during transportation from sampling site to laboratory were small. The precision of counting spore-containing particles by LM and SEM was better than that of counting individual spores. No such difference was found for FM because many large spore-containing particles were dispersed during preparation.