Biomedical subjects

D Heederik

Publications and source records attributed to D Heederik.

At least 73 records · Page 4Linked to original sources

PubMed1998

Occupational respiratory allergy in bakery workers: a review of the literature.

Baker's asthma has long been recognized as a serious disease among workers in the bakery industry and the number of cases with baker's asthma is steadily increasing. This paper presents a review of the available literature on baker's allergy with a special focus on the allergens involved, the epidemiologic research and issues on exposure assessment, evidence of exposure-response-relationships, and possible prevention strategies. A large number of potential allergens have been identified and are described here. At present little is known about the incidence of baker's allergy. On the other hand, a large number of cross-sectional studies have been performed, showing that sensitization and work-related symptoms are common among bakery workers. Only atopy and exposure level have consistently been reported as determinants of this occupational disease. Age, gender, and smoking habits do not seem to be associated with sensitization or work-related respiratory symptoms. Recently, immunochemical methods have been developed to measure specific allergens in the bakery industry, which have been used to unravel the role of allergen exposure in the development of baker's asthma. Clear exposure-response-relationships have been found. The implications of these recent findings for prevention strategies and standard setting are discussed.

Allergens↗

PubMed1998

Individual-based and group-based occupational exposure assessment: some equations to evaluate different strategies.

Basically, two strategies can be considered for the analysis of hazardous pollutants in the work environment: group-based and individual-based strategies. This paper provides existing and recently derived equations for both strategies describing the influence of several factors on attenuation and on the standard error of an estimated linear regression coefficient relating a continuous exposure variable and a continuous health outcome via a simple linear regression model. We applied these equations using exposure variability information from industry-wide surveys over the past decade in order to gain more insight into the effects of various sources of exposure variability on choices among different analysis strategies. In general, for the modeling scenario considered here, there is not a straightforward criterion for choosing an optimal analysis strategy. Researchers have to decide between individual-based strategies generating precise, though biased, estimates or group-based strategies generating less precise but essentially unbiased estimates. For most exposure variability scenarios evaluated, an individual-based strategy yielded substantial attenuation. It is the authors' contention that the choice between individual-based and group-based strategies should be based on validity, rather than on precision, of the estimated exposure-response coefficient.

Air Pollutants, Occupational↗

PubMed1998

Fruit and fish consumption: a possible explanation for population differences in COPD mortality (The Seven Countries Study).

OBJECTIVE: To investigate whether average intake of antioxidants, fruits, vegetables and fish may help to explain international differences in chronic obstructive pulmonary disease (COPD) mortality. DESIGN: Ecological analysis using information on baseline diet and the 25-year COPD mortality rate in the 16 cohorts of the Seven Countries Study. SETTING: Population-based cohorts. SUBJECTS: Men aged 40-59 years at baseline. METHODS: Dietary information was collected at baseline in small random samples of each cohort. In 1987 the reported foods were bought locally and analysed chemically. After 25 years of follow-up the underlying cause of death of those who died was established centrally. COPD mortality rate ratios were calculated, for a change equivalent to 10% of the overall mean consumption of a dietary factor. RESULTS: We observed independent inverse associations between 25-year COPD mortality and baseline consumption of fruits (rate ratio 0.49; 95% confidence interval 0.36-0.67) and fish (rate ratio, 0.97; 95% confidence interval 0.93-1.00), after adjustment for potential confounders. COPD mortality showed no statistically significant association with intake of antioxidants or vegetables. Fruit and fish consumption together explained about 67% of the variance in the COPD mortality rates of the cohorts. CONCLUSIONS: Fruit and fish consumption may partly explain population differences in COPD mortality. This is in accordance with suggestions for a relationship between fruit and fish consumption and COPD observed in studies in individuals.

Adult↗

PubMed1998

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.

Aerosols↗

PubMed1998

Exposure to captan in fruit growing.

This study characterized occupational exposure to pesticides in fruit growing in The Netherlands to assess determinants of exposure. Large-scale exposure surveys were carried out during application of pesticides and during reentry activities. Data on contamination inside the fruit growers' homes were obtained, and total potential exposure for the fruit grower and his family during the growing and harvesting season was estimated. Repeated measurements on the same subject were collected to study components of exposure variability. Relative contribution of the respiratory route and different skin sites to total exposure were assessed. Captan was used as a marker for exposure. Inhalable dust exposure was measured with a personal monitor and potential dermal exposure with skin pads and hand rinsing. Dislodgeable foliar residue was measured by taking leaf punches. For respiratory exposure and potential dermal exposure, differences were observed between several tasks. Workers were categorized according to tasks performed depending on the exposure measure(s) (e.g., hands, forehead, inhalable dust) considered relevant for a specific study purpose. In general, within-worker variability of all exposure measurements was larger than between-worker variability. Variability in dermal exposure on the same body location was small relative to variability between different body locations. Differences in total exposure, including exposure inside the home, between the fruit grower and the son were small. Exposure of the wife was two to three times lower than for the fruit grower and the son. As exposure per unit of time was in the same order of magnitude for different tasks, individual time spent on these tasks is crucial for estimating total potential exposure. Repeated measurements are necessary to estimate individual exposure accurately because of the large within-worker variability.

Adolescent↗

PubMed1998

Determinants of exposure to captan in fruit growing.

A series of studies investigated occupational exposure to pesticides among fruit growers in The Netherlands during spraying and reentry of orchards between 1990 and 1992 to identify and quantify determinants of exposure. Determinants of exposure are discussed as a starting point for hazard identification and control. Captan was used as a marker for exposure. Cabin use of the tractor was the most prominent determinant of dermal exposure during spraying. For respiratory exposure, factors related to preparation of pesticides were most prominent. A long duration of exposure may reflect a different exposure situation compared with a short duration of exposure. As different determinants of exposure prevailed for each subgroup, consideration should be given to constructing exposure models for each group separately. Dislodgeable foliar residue (DFR) was the most prominent determinant of exposure for both respiratory and dermal exposure during reentry. However, no significant relation between DFR and dermal exposure of forehead and sternal area was found, perhaps because there was no direct contact with foliage here. Therefore, use of a transfer factor based on DFR to estimate total dermal exposure is only a crude estimate. The half-life of captan on crops varied from 10-17 days, so substantial exposure when entering the orchard is very likely, particularly when spraying frequency is high. The main starting points for reduction of exposure are use of a cabin, DFR, and individual time spent on different tasks. Determinants that are constant over time (cabin use) may have an especially great influence on grouping workers, according to long-term exposure in epidemiological studies. As determinants of exposure vary for the different exposure routes and body locations (for dermal exposure), the measure of interest for a specific study design will decide which determinants are most relevant.

Adult↗

PubMed1998

Between- and within-observer agreement for expert judgment of peak flow graphs from a working population.

Expert judgment of peak flow-time graphs provides an important tool to detect occupational asthma. This technique has mainly been used in clinics to evaluate reversible airflow obstruction and to assess potential work-related patterns. The reproducibility of this technique in an open working population is unknown. Agreement between and within nine experts was studied using peak flow-time graphs of 49 potato-processing workers. All graphs were classified into four categories by the nine experts, while seven experts read ten graphs at two occasions. Thirty-four graphs (69%) were classified as "no airway obstruction" while four graphs (8%) showed "work-related airway obstruction." There was only slight agreement between the nine experts; mean Cohen's kappa (kappa) was 0.19. Agreement within experts was moderate; mean kappa was 0.47 for judging graphs twice. Our results suggest that in a "healthy" working population, judgment of peak flow graphs is not a favorable method for detection of airway obstruction. If this technique is applied in epidemiological studies, judgment of the graphs should be done by more than one expert.

Adult↗

PubMed1998

Evaluation of chronic respiratory effects in the potato processing industry: indications of a healthy worker effect?

OBJECTIVE: To investigate the occurrence of chronic respiratory effects of exposure to organic dust in the potato processing industry. METHODS: Self reported chronic respiratory symptoms and spirometric lung function were assessed in a cross sectional study among 135 potato processing workers. A comprehensive study of current exposure to dust, endotoxin, and potato antigens had been performed previously. Workers were grouped into low and high exposure categories for each of the three exposure indices. Relations between exposure concentrations and respiratory health variables were investigated either by calculating prevalence rate ratios or by performing linear regression analyses. Atopy was assessed by measuring total immunoglobulin E (IgE) and specific IgE to five common aeroallergens in serum samples of workers. RESULTS: Evident relations between current exposure indices and respiratory health in the entire group were not found. Workers employed < or = 5 years showed a two-fold higher prevalence of respiratory symptoms, lower lung function, and higher endotoxin exposure than workers employed for > 5 years. Also, atopy was more prevalent in workers employed < or = 5 years. After stratification for duration of employment, negative effects of endotoxin on lung function among workers employed < or = 5 years were suggested. CONCLUSIONS: This study does not show chronic respiratory effects of exposure to organic dust in the potato processing industry, despite the fact that the levels of exposure to endotoxin found in this industry have been reported to be associated with decreases in lung function in other occupational settings. A likely explanation for not detecting apparent effects might be that many symptomatic workers drop out of this industry a few years after starting the job, suggesting a healthy worker effect.

Adult↗

PubMed1998

Stepwise health surveillance for bronchial irritability syndrome in workers at risk of occupational respiratory disease.

OBJECTIVES: Questionnaires, lung function tests, and peak flow measurements are widely used in occupational health care to screen for subjects with respiratory disease. However, the diagnostic performance of these tests is often poor. Application of these tests in a stepwise manner would presumably result in a better characterisation of subjects with respiratory disease. METHODS: Cross sectional data from workers exposed to acid anhydrides, to laboratory animals, and to flour dusts were used. Sensitivity and specificity were calculated from cross tables of different (combinations of) tests for bronchial hyperresponsiveness and bronchial irritability in the past four weeks (BIS). From sensitivity and specificity likelihood ratios were computed and change in probability of BIS was calculated. RESULTS: The prevalence of BIS was 7%, 7%, and 5%, respectively. In all groups questionnaire data provided excellent sensitivity but poor specificity, which was inherent on the broad definition of symptoms. Adding the forced expiratory volume in one second/forced vital capacity (FEV1/FVC) ratio yields almost perfect specificity, and peak expiratory flow (PEF) variability is intermediate in populations in which smoking induced or non-allergic respiratory diseases predominates. In occupational groups in which asthma is a problem, adding PEF measurements will optimise sensitivity and specificity in detection of BIS. The probability of BIS for subjects with a negative combined test outcome was lower than the probability before testing. Subjects with a positive combined test outcome had a probability of BIS after the tests at least three times the probability before. CONCLUSIONS: Combined testing yields better sensitivity and specificity. An advantage of combined testing is an economy in the effort to screen for subjects with BIS. Combined testing resulted in more detailed estimation of the probability of BIS.

Anhydrides↗

PubMed1998

Decline in lung function related to exposure and selection processes among workers in the grain processing and animal feed industry.

OBJECTIVES: To follow up workers in the grain processing and animal feed industry five years after an initial survey, and to monitor exposures to organic dust and endotoxin and changes in prevalence of respiratory symptoms and lung function. METHODS: Outcome measures in the present survey were decline in lung function over five years, rapid annual decline in forced expiratory volume in one second (FEV1) above 90 ml.s-1, and loss to follow up. RESULTS: Among 140 workers included in the longitudinal analysis, annual decline in FEV1 and maximal mid-expiratory flow (MMEF) were significantly related to occupational exposure to dust and endotoxin in the grain processing and animal feed industry. Assuming a cumulative exposure over a working life of 40 years with an exposure of 5 mg.m-3, the estimated effect on the FEV1 would be a decline of 157 ml.s-1 (95% CI 13 to 300)--that is, about 4% of the group mean FEV1 and 473 ml.s-1 (95% CI 127 to 800) of the MMEF (about 12%). Workers with a dust exposure > 4 mg.m-3 or endotoxin concentrations > 20 ng.m-3 at the 1986-8 survey had significantly higher risk of rapid decline in FEV1 (odds ratio (OR) 3.3, 95% CI 1.02 to 10.3). The relations between occupational exposure and decline in lung function in this study occurred, despite the selection through the healthy worker effect that occurred as well. Increasing working years was related to decreasing annual decline in FEV1 and fewer people with rapid decline in FEV1 (OR 0.04, 95% CI 0 to 0.61 for over 20 v < 5 working years in the grain processing and animal feed industry). The presence of respiratory symptoms at baseline was a strong predictor of subsequent loss to follow up. Baseline lung function was not found to be predictive of subsequent loss to follow up. However, among workers lost to follow up the number of working years was more strongly negatively related to baseline lung function than among the workers who were studied longitudinally. CONCLUSIONS: The existence of the healthy worker effect implies that an exposure-response relation in the grain processing and animal feed industry may well be underestimated. This should be taken into account when health based recommended limit values are to be developed.

Adult↗

PubMed1998

Endotoxin exposure as a major determinant of lung function decline in pig farmers.

Exposure-response relationships for endotoxin as measured in dust and longitudinal decline in lung function were studied. A cohort of 171 pig farmers was followed over a 3-yr period. Long-term average exposure to dust and endotoxin was determined by personal monitoring in summer and winter, using data on farm characteristics and activities. Mean decline in FEV1 was 73 ml/yr and in FVC 55 ml/ yr. Long-term average exposure to dust was 2.63 mg/m3 (geometric SD [GSD] 1.30), and to endotoxin, 105 ng/m3 (GSD 1.5). Annual decline in FEV1 was significantly associated with endotoxin exposure. An increase in exposure with a factor 2 was associated with an extra decline of FEV1 of 19 ml/yr.

Adult↗

PubMed1998

Wheat sensitization and work-related symptoms in the baking industry are preventable. An epidemiologic study.

A cross-sectional study was conducted among 393 workers from 21 bakeries to study the relationship between wheat allergen exposure and wheat sensitization and work-related allergic symptoms. Exposure to wheat allergens was characterized by a recently developed and validated immunoassay. Specific IgE antibodies against wheat flour and common allergens were measured by immunoassays, and work-related allergic symptoms were registered by questionnaire. A strong and positive association was found between wheat flour allergen exposure and wheat flour sensitization. This relationship was steepest and strongest in atopics. Prevalence ratios for high and medium wheat allergen exposure were 5.2 (95% confidence interval [CI], 1.6-16.2), and 2.7 (0.5-14.5) for atopic workers, and 2.5 (0.8-7.5) and 1.4 (0. 3-6.4) for nonatopics, compared with workers with low wheat allergen exposure. In sensitized bakers those with an elevated allergen exposure had more often work-related symptoms, with prevalence ratios for high and medium wheat allergen exposure of 3.5 (CI 1.6-7. 5) and 2.6 (CI 0.9-7.8), respectively, compared with workers with low wheat allergen exposure. The existence of exposure-sensitization gradients suggests that work-related sensitization risk will be negligible when exposure levels will be reduced to average exposure concentration of 0.2 microgram/m3 wheat allergen or approximately 0.5 mg/m3 inhalable dust during a work shift.

Adult↗

PubMed1998

Work-related changes in peak expiratory flow among laboratory animal workers.

Laboratory animal workers are at risk of developing allergic symptoms, of which asthmatic symptoms are the most severe. The aim was to study the relationship between allergic symptoms due to working with rats and variability and changes in peak expiratory flow (PEF). Several indices were used on the basis of the amplitude of the PEF or the differences in PEF between days with and without exposure to rat aeroallergens. Of the 398 rat workers, 73% completed PEF readings on at least 9 days, of whom 208 had PEF readings on working days with and without contact with animals. The overall prevalence rate of allergic symptoms (asthmatic, eye, nose and/or skin) among rat workers during the handling of rats was 17.3%. Asthmatic symptoms were reported by 6.7%. The PEF of the workers who reported asthmatic symptoms due to working with rats decreased significantly on days working with the animals (difference between the minimum PEF averaged over working days with animals and over days without animals (deltaPEFmin-min) = -73 L x min(-1)), compared to the workers without symptoms (2.2 L x min(-1)). This effect was more pronounced among workers with a late asthmatic response, i.e. the presence of asthmatic symptoms several hours after working with rats (deltaPEFmin-min = -11.6 L x min(-1)). Multiple regression analyses showed that only those with asthmatic symptoms several hours after working with rats and those with allergic symptoms had an increased deltaPEFmin-min. In addition, workers with asthmatic symptoms were also more likely to have a higher PEF variability than workers without asthmatic symptoms. However, no difference in PEF variability between days with and without animals contact was observed. This study shows that the peak expiratory flow of workers who reported asthmatic symptoms due to working with rats decreased significantly on days working with laboratory animals.

Adult↗

PubMed1998

Determinants of airborne rat and mouse urinary allergen exposure.

OBJECTIVES: The purpose of this study was to determine the factors affecting exposure to rat and mouse urinary allergens. METHODS: Ambient and personal air sampling was performed on a large scale in 7 laboratory animal facilities. RESULTS: Allergens were mainly present as large particles (>5.8 microm). The higher the number of animals in a room, the higher the allergen concentrations. Allergen levels were twice as high on Mondays as on other days due to the tasks performed on Mondays. Filter tops on animal cages were associated with 6-17 times lower ambient allergen levels. An inverse day-night rhythm for rats produced > or = 10 times higher rat urinary allergen levels. Personal exposure to rat and mouse urinary allergens differed between job titles but especially between facilities, probably because of differences in task performance and technology. Task-specific sampling revealed that the highest personal exposure levels occurred when contaminated bedding and high numbers of conscious animals were handled. The proportion of time spent on these tasks determined the degree of allergen exposure to a large extent. CONCLUSIONS: This study showed that the number of animals present in the room, use of filter top cages, and an inverse day-night rhythm were important determinants of rat and mouse urinary allergens in ambient air. Personal exposure to rat and mouse urinary allergens was predominantly determined by the task and site and, to a limited extent, by ambient exposure levels. The presented determinants can be used to develop exposure reduction strategies and also to aid epidemiologic studies of laboratory animal allergy.

Air Pollution, Indoor↗

PubMed1998

[Quantification of inhaled exposure to alpha-amylase in 2 bakeries].

BACKGROUND: Baker's asthma and baker's rhinitis are among the most frequent occupational diseases. A major cause is the high exposure to flour dust in the workplace and to allergenic enzymes like alpha-amylase from Aspergillus oryzae (allergen name: Asp o 2). METHODS: To quantify allergen exposure in the workplace, 31 personal dust samples in a conventional small bakery (six workers) and in a biobakery (seven workers) were collected. Using a recently developed two-site enzyme-linked immunosorbent assay based on monoclonal antibodies to alpha-amylase from Aspergillus oryzae, the allergen content of these dust samples was determined. RESULTS: Dust exposure in the biobakery was in the range between 3.5 and 12 mg/m3 (median: 5.2 mg/m3) and in the conventional bakery between 0.9 and 118 mg/m3 (median 8.5 mg/m3). 23 out of 31 exposure measurements showed values higher than 4 mg/m3 (threshold limit value for inhalable dust). In the biobakery, no fungal alpha-amylase could be detected. 15 out of 17 samples taken in the conventional bakery contained fungal alpha-amylase in the range between 0.2 and 88 ng per mg dust. The geometric mean of alpha-amylase exposure in this bakery was 13 ng Asp o 2/m3, and the maximum exposure was 4.8 micrograms/m3. In four cases, fungal alpha-amylase was detected although exposure to dust was below the threshold limit of 4 mg/m3. CONCLUSIONS: This study in two German bakeries shows that preventive measures to reduce contact to allergens have not been sufficiently realised. Relevant alpha-amylase exposure occurred at low dust levels illustrating that dust measurements are not adequate to control alpha-amylase exposure. For fungal alpha-amylase an additional threshold limit should be established.

Aspergillus oryzae↗

PubMed1997

Grouping strategies for exposure to inhalable dust, wheat allergens and alpha-amylase allergens in bakeries.

This paper describes repeated measurements of inhalable flour dust, wheat allergens and alpha-amylase allergens in the bakery industry. A total of 571 full-shift personal dust samples was collected. Wheat allergens and alpha-amylase allergens were measured in 449 and 507 samples, respectively, by the use of recently developed immunoassays. For all three measures of exposure, the main components of exposure variability were determined. Different grouping strategies for studying exposure-response relationships were compared. The specific job of a bakery worker was identified as the most important source of variability in inhalable flour dust concentrations. For exposure to wheat allergens, the job performed was also the most important source of variation, but type of bakery also explained some of the variability. For alpha-amylase allergen exposure, information on type of bakery was more important then job information. For exposure to inhalable dust and wheat allergens, a classification by job title would lead to sufficient contrast in average exposure levels. By contrast, a grouping strategy based on a combination of job and type of bakery appeared to be essential to obtain a useful classification of exposure to alpha-amylase allergens. 1997 British Occupational Hygiene Society.

Allergens↗

PubMed1997

Airborne levels of alpha-amylase allergens in bakeries.

BACKGROUND: In the baking industry the use of enzymes has increased throughout the 1980s. Several studies have reported sensitization and respiratory disorders among bakery workers caused by enzymes in dough improvers. Fungal alpha-amylase is the most frequently reported cause of allergy. alpha-Amylase allergen exposure levels in the bakery industry, however, have not yet been reported. OBJECTIVE: The main objective of this study was to quantify personal alpha-amylase exposure levels of bakery workers. METHODS: alpha-Amylase allergens were measured in 507 personal samples of airborne dust taken in bakeries by using a newly developed sandwich enzyme immunoassay with affinity-purified polyclonal rabbit IgG antibodies. A cascade impactor was used to estimate the size of dust particles carrying alpha-amylase allergens. RESULTS: The rabbit IgG antibodies used in the assay showed, in immunoblotting with commercially available alpha-amylase, a reaction profile very similar to that of IgE from sensitized bakers. The enzyme immunoassay appeared to be highly specific for fungal amylase. Allergen exposure levels varied considerably among bakery workers, depending on the type of bakery and job category (range, 0 to 40 ng/m3). In confectioneries no alpha-amylase allergens were detected. In other bakeries alpha-amylase exposure was only found for workers directly involved in dough making. Measurements of the particle size distribution in these bakeries showed that alpha-amylase allergens are most likely to be deposited in the nose and ciliated airways. CONCLUSION: This study shows that personal monitoring of fungal amylase allergen exposure in bakeries is possible. This permits the identification of high-risk tasks and allergen sources, as well as the study of exposure-response relationships.

Air Pollutants, Occupational↗

PubMed1997

Intraindividual variability and redundancy of semen parameters.

We analyzed two databases comprising repeated semen analyses of male patients visiting a fertility clinic in the Netherlands to assess intra- and interindividual variability for several semen parameters. We calculated reliability coefficients to estimate the attenuation of the slope if semen parameters are used to predict the probability of conception in regression models. Reliability was lowest for morphology (Population A: R = 0.48, Population B: R = 0.54), but somewhat better for motility (Population A: R = 0.66, Population B: R = 0.71) and count (Population A: R = 0.79, Population B: R = 0.81). Semen concentration had the largest reliability coefficients (Population A: R = 0.84, Population B: R = 0.84). Stimulations using empirical variance components indicated that using semen parameters as endpoints in case-referent studies might substantially underestimate measures of association. The results showed that most semen parameters were just moderately redundant (range: Kappa = 0.28 to Kappa = 0.45); only agreement between concentration and count was substantial (Population A: Kappa = 0.84, Population B: Kappa = 0.80). Hence, epidemiologic studies focusing on male infertility should take into account a variety of parameters.

Analysis of Variance↗