Occupational exposure to respirable crystalline silica and incident idiopathic interstitial pneumonias and pulmonary sarcoidosis: a national prospective follow-up study.

BACKGROUND: Respirable crystalline silica is a well-known cause of silicosis but may also be associated with other types of interstitial lung disease. We examined the associations between occupational exposure to respirable crystalline silica and the risk of idiopathic interstitial pneumonias, pulmonary sarcoidosis and silicosis. METHODS: The total Danish working population was followed 1977-2015. Annual individual exposure to respirable crystalline silica was estimated using a quantitative job exposure matrix. Cases were identified in the Danish National Patient Register. We conducted adjusted analyses of exposure-response relations between cumulative silica exposure and other exposure metrics and idiopathic interstitial pneumonias, pulmonary sarcoidosis and silicosis. RESULTS: Mean cumulative exposure was 125 µg/m3-years among exposed workers. We observed increasing incidence rate ratios with increasing cumulative silica exposure for idiopathic interstitial pneumonias, pulmonary sarcoidosis and silicosis. For idiopathic interstitial pneumonias and pulmonary sarcoidosis, trends per 50 µg/m3-years were 1.03 (95% CI 1.02 to 1.03) and 1.06 (95% CI 1.04 to 1.07), respectively. For silicosis, we observed the well-known exposure-response relation with a trend per 50 µg/m3-years of 1.20 (95% CI 1.17 to 1.23). CONCLUSION: This study suggests that silica inhalation may be related to pulmonary sarcoidosis and idiopathic interstitial pneumonias, though these findings may to some extent be explained by diagnostic misclassification. The observed exposure-response relations for silicosis at lower cumulative exposure levels than previously reported need to be corroborated in analyses that address the limitations of this study.

Occupational exposure to epoxy components and risk of dermatitis: A registry-based follow-up study of the wind turbine industry.

BACKGROUND: Allergic contact allergy and dermatitis are frequently reported among epoxy-exposed workers. OBJECTIVES: To determine the risk of dermatitis associated with epoxy exposure. METHODS: We followed 825 epoxy-exposed and 1091 non-exposed blue-collar workers, and 493 white-collar workers of a Danish wind turbine blade factory during 2017-2022 with linked data from national health registers on diagnoses, patch testing, or fillings of prescriptions for topical corticosteroids. Incidence rate ratios of dermatitis or a first-time topical corticosteroid prescription were estimated with Poisson regression using non-exposed blue-collar workers as reference. We similarly estimated incidence rate ratios for the duration of epoxy exposure and current epoxy exposure. RESULTS: Epoxy-exposed blue-collar workers showed a dermatitis incidence rate of 2.1 per 100 000 person days, a two-fold increased risk of dermatitis and a 20% increased risk of filling a prescription for topical corticosteroids. Incidence rate ratios were higher during early exposure and declined with further exposure for both outcomes. White-collar workers had generally lower risks. CONCLUSION: We observed an increased risk of dermatitis following epoxy exposure confirming previous case reports and cross-sectional studies emphasizing the need for intensified focus on preventive efforts for this group of workers.

Prevalence of skin sensitization and dermatitis among epoxy-exposed workers in the wind turbine industry.

BACKGROUND: A high prevalence of skin sensitization and dermatitis has been reported among workers exposed to epoxy components. OBJECTIVES: To estimate the risk of skin sensitization and dermatitis among workers exposed to epoxy components during production of wind turbine blades while using comprehensive safety measures. METHODS: A cross-sectional study of 180 highly epoxy-exposed production workers and 41 nonexposed office workers was conducted at two wind turbine blade factories in Denmark. Participants underwent a skin examination, were tested with a tailored patch test panel including epoxy-containing products used at the factories, and answered a questionnaire. RESULTS: Sixteen production workers (8·9%) were sensitized to an epoxy component compared with none of the office workers. Skin sensitization was more frequent within the first year of exposed employment. Strong selection bias by atopic status was indicated. Among nonatopic workers, the prevalence of dermatitis was higher among production workers (16·4%) than among office workers [6·5%, odds ratio (OR) 2·3, 95% confidence interval (CI) 0·6-9·1] and higher among the sensitized workers (43·8%) than the nonsensitized workers (14·6%, OR 4·5, 95% CI 1·6-12·7). Resins based on diglycidyl ether of bisphenol A and F were the most frequent sensitizers. One of the four workers sensitized to epoxy components used at the factories did not react to the epoxy resin of the TRUE test® panel. CONCLUSIONS: Despite comprehensive skin protection, sensitization and dermatitis are prevalent among highly epoxy-exposed workers in the wind turbine industry in Denmark. Our findings document the need for intensified preventive efforts and emphasize the importance of tailored patch testing. What is already known about this topic? Epoxy components are well-known sensitizers of the skin. A high prevalence of skin sensitization and dermatitis has been reported among workers exposed to epoxy components. Comprehensive protective equipment is recommended when working with epoxy components. What does this study add? Despite comprehensive skin protection, skin sensitization and dermatitis are prevalent among epoxy-exposed workers. We found that 40% of workers sensitized to epoxy products had dermatitis. Only 75% of the sensitized workers were detected by the epoxy resin of the TRUE test® , which emphasizes the importance of tailored testing.

Association of perceived work pace and physical work demands with occupational accidents: a cross-sectional study of ageing male construction workers in Denmark.

BACKGROUND: Occupational accidents continue to be a significant public health challenge worldwide. Construction workers in particular are at high risk of occupational accidents, and thus it is of major importance to identify possible predictors of occupational accidents among construction workers. We aimed to investigate the association between self-reported work pace and physical work demands and occupational accidents among ageing male construction workers in Denmark. METHODS: Data on perceived work pace, physical work demands, and occupational accidents was acquired from questionnaires sent to ageing construction workers in Denmark in 2016 as part of the ALFA project (ALdring og Fysisk Arbejde; Ageing and Physical Work). A sample of 1270 Danish male construction workers above 50 years of age was included in the present study. Multiple logistic regression models were applied, with adjustments for age, smoking, body mass index, musculoskeletal disorders, occupation, work experience, and support at work. RESULTS: Of 1270 construction workers, 166 (13.1%) reported an occupational accident within the last 12 months. There was no significant association between perceived work pace and occupational accidents, but physical work demands were associated with higher odds for occupational accidents, with an odds ratio of 2.27 (95% confidence interval 1.26-4.10) for medium physical work demands and 2.62 (95% confidence interval 1.50-4.57) for high physical work demands. CONCLUSIONS: Ageing male construction workers with high physical work demands had statistically significant higher odds of having an occupational accident. By contrast, perceived work pace was not associated with occupational accidents in this large cross-sectional study.

Retirement status and frailty: a cross-sectional study of the phenotype of manual workers aged 50-70 years.

BACKGROUND: The frailty phenotype is predictive of mortality and has been identified in the working population. This cross-sectional study aimed to investigate the prevalence of frailty and individual frailty symptoms among active and retired Danish manual workers and to delineate the relationship between frailty and lifestyle factors. METHODS: Manual workers aged 50-70 years answered questions relating to the Fried criteria for frailty (weight loss, exhaustion, slowness, weakness and inactivity). Only men were included in the analyses and respondents were stratified according to work status: active workers (n = 1555), early retirees (n = 289) and workers retired at or after normal pension age (n = 291). Associations between pre-frailty/frailty, work status and various lifestyle factors were estimated using binomial logistic regression. RESULTS: Overall, the prevalence of pre-frailty (one or two symptoms) and frailty (three or more symptoms) was 33.3% and 1.5%, respectively. Those who had retired early were more likely to be pre-frail/frail compared with active workers (odds ratio 2.20, 95% CI 1.61-3.01). Exhaustion was the most prominent symptom reported by 22.2% of active workers, 34.6% of early retirees and 16.5% of workers retired at normal retirement age. Lifestyle factors including obesity, physical inactivity and smoking but not alcohol intake were associated with pre-frailty/frailty. CONCLUSION: Symptoms of frailty are identifiable and present among both active and retired manual workers. Data suggest discrepancies among Danish manual workers, with some having unhealthy lifestyles and being more prone to develop pre-frailty and frailty already in their sixth decade of life.

Physical-work ability and chronic musculoskeletal complaints are related to leisure-time physical activity: Cross-sectional study among manual workers aged 50-70 years.

AIMS: To investigate the associations between both high- and low-intensity leisure-time physical activity on physical-work ability and chronic musculoskeletal complaints among manual workers aged 50-70 years. METHODS: In this cross-sectional study, 1763 manual workers (mean age 57.1, SD ± 4.7 years) replied to questions about leisure-time physical activity, physical-work ability, chronic musculoskeletal complaints as well as health and lifestyle factors. Ordinal and binomial logistic regression models were constructed to assess the influence of the duration of both low- and high-intensity physical activity on physical-work ability and chronic musculoskeletal complaints, respectively. Models were adjusted for gender, age, smoking, alcohol intake, body mass index, physical-work demand, work experience, chronic disease and, regarding physical-work ability, also for chronic musculoskeletal complaints. RESULTS: A statistically significant association between greater physical-work ability and high-intensity physical activity was found for workers engaged in 3-4 h/wk and ⩾ 5 h/wk (OR 1.59, 95% CI 1.15-2.19 and OR 1.56, 95% CI 1.10-2.22, respectively). For both high- and low-intensity physical activity, a duration of 3-4 h/wk was associated with lower odds of reporting chronic musculoskeletal complaints in the knees (OR 0.65, 95% CI 0.42-1.00 and OR 0.61, 95% CI 0.38-0.99, respectively). CONCLUSIONS: Engaging in ⩾ 3 h/wk of high-intensity leisure-time physical activity was associated with greater physical-work ability among manual workers aged 50-70 years. Both high- and low-intensity physical activity related to lower odds of having chronic musculoskeletal complaints in the knees.

Feedback on Measured Dust Concentrations Reduces Exposure Levels Among Farmers.

BACKGROUND: The high burden of exposure to organic dust among livestock farmers warrants the establishment of effective preventive and exposure control strategies for these workers. The number of intervention studies exploring the effectiveness of exposure reduction strategies through the use of objective measurements has been limited. OBJECTIVE: To examine whether dust exposure can be reduced by providing feedback to the farmers concerning measurements of the exposure to dust in their farm. METHODS: The personal dust levels of farmers in 54 pig and 26 dairy cattle farms were evaluated in two measurement series performed approximately 6 months apart. Detailed information on work tasks and farm characteristics during the measurements were registered. Participating farms were randomized a priori to a control (n = 40) and an intervention group (n = 40). Shortly after the first visit, owners of intervention farms only received a letter with information on the measured dust concentrations in the farm together with some general advises on exposure reduction strategies (e.g. use of respirators during certain tasks). Relationships between measured dust concentrations and intervention status were quantified by means of linear mixed effect analysis with farm and worker id as random effects. Season, type of farming, and work tasks were treated as fixed effects. Changes in exposure over time were explored primarily at a farm level in models combined, as well as separate for pig and cattle farmers. RESULTS: After adjustment for fixed effects, an overall reduction of 23% in personal dust exposures was estimated as a result of the intervention (P = 0.02). Exposure reductions attributable to the intervention were similar across pig and cattle farmers, but statistically significant only for pig farmers. Intervention effects among pig farmers did not depend on the individuals' information status; but among cattle farmers a significant 48% reduction in exposure was found only among individuals that reported to have been informed. No systematic differences in changes over time considering the use of respiratory protection between the intervention and control groups were observed. CONCLUSION: The results of the present study suggest reductions between 20 and 30% in personal exposure to inhalable dust to be feasible through simple information provided to the farm owners regarding actual levels of exposure together with instructions on basic measures of prevention. The exact reasons for these effects are unclear, but likely they involve changes in behavior and working practices among intervention farmers.

Health impacts of anthropogenic biomass burning in the developed world.

Climate change policies have stimulated a shift towards renewable energy sources such as biomass. The economic crisis of 2008 has also increased the practice of household biomass burning as it is often cheaper than using oil, gas or electricity for heating. As a result, household biomass combustion is becoming an important source of air pollutants in the European Union.This position paper discusses the contribution of biomass combustion to pollution levels in Europe, and the emerging evidence on the adverse health effects of biomass combustion products.Epidemiological studies in the developed world have documented associations between indoor and outdoor exposure to biomass combustion products and a range of adverse health effects. A conservative estimate of the current contribution of biomass smoke to premature mortality in Europe amounts to at least 40 000 deaths per year.We conclude that emissions from current biomass combustion products negatively affect respiratory and, possibly, cardiovascular health in Europe. Biomass combustion emissions, in contrast to emissions from most other sources of air pollution, are increasing. More needs to be done to further document the health effects of biomass combustion in Europe, and to reduce emissions of harmful biomass combustion products to protect public health.

The asbestos-asbestosis exposure-response relationship: a cohort study of the general working population.

OBJECTIVES: The association between asbestos exposure and asbestosis in high-exposed industrial cohorts is well-known, but there is a lack of knowledge about the exposure-response relationship for asbestosis in a general working population setting. We examined the exposure-response relationship between occupational asbestos exposure and asbestosis in asbestos-exposed workers of the Danish general working population. METHODS: We followed all asbestos-exposed workers from 1979 to 2015 and identified incident cases of asbestosis using the Danish National Patient Register. Individual asbestos exposure was estimated with a quantitative job exposure matrix (SYN-JEM) from 1976 onwards and back-extrapolated to age 16 for those exposed in 1976. Exposure-response relations for cumulative exposure and other exposure metrics were analyzed using a discrete time hazard model and adjusted for potential confounders. RESULTS: The range of cumulative exposure in the population was 0.001 to 18 fibers per milliliter-year (f/ml-year). We found increasing incidence rate ratios (IRR) of asbestosis with increasing cumulative asbestos exposure with a fully adjusted IRR per 1 f/ml-years of 1.18 [95% confidence interval (CI) 1.15- -1.22]. The IRR was 1.94 (95% CI 1.53-2.47) in the highest compared to the lowest exposure tertile. We similarly observed increasing risk with increasing cumulative exposure in the inception population. CONCLUSIONS: This study found exposure-response relations between cumulative asbestos exposure and incident asbestosis in the Danish general working population with mainly low-level exposed occupations, but there is some uncertainty regarding the exposure levels.

Air pollution, climate change, and health.

Air pollution causes premature mortality and increased morbidity in Denmark as well as worldwide. This review investigates how the climate changes contribute to these through e.g., wildfires and increased levels of ozone. Air pollution and climate gases share sources such as burning of fossil fuels and biomass and thus a reduction in the use of these will improve health, mitigate climate change, and reduce societal costs simultaneously. The costs of actions against climate change could thus be reduced.

Heatwaves and association with comorbidities, pharmacotherapy, and mortality.

Heatwaves are getting more common and is the largest weather-related cause of death in high-income countries. A summary of some of the implications is given in this review. Most of the excess mortality is preventable. However, there is need for increased preparedness and awareness. Common non-communicable diseases increase the risk of unfavorable outcome in relation to heatwave, and many commonly prescribed medications affect the heat regulatory system with increasing evidence for increased hospitalisation and mortality. There is an urgent need for further research on heatwaves effect on prescribed medication and mortality.

How to account for Inuit ancestry in lung function prediction.

Rigorous lung function prediction equations for the Inuit are lacking. We used spirometry from 351 Inuit and 29 people of other ancestry obtained during an occupational survey in Greenland to determine how to obtain valid lung function predictions for the Inuit using Global Lung Function Initiative (GLI) equations for Europeans. Standing height for the Inuit was used in the predictions as well as their height modified in line with the known differences in standing to sitting height ratio (SHR) for the Inuit. With recorded height in predicting lung function, mean±SD Inuit z-scores for FVC and FEV1 were significantly higher than predicted (0.81±1.20 and 0.53±1.36, respectively, p<0.0001) which was not true for the non-Inuit participants (-0.01±1.04 and 0.15±1.17, respectively). When using height modified for SHR the mean±SD Inuit z-scores for FVC and FEV1 were no longer significantly different from predicted (0.10±1.10 and -0.12±1.24, respectively). The mean±SD Inuit FEV1/FVC z-scores were not significantly different from the non-Inuit, being respectively -0.45±0.98 and -0.01±1.04. Modified height changed the mean±SD Inuit FEV1/FVC z-scores to -0.39±0.99. Representative lung function predictions from GLI equations can be made for Inuit by using standing height modified for the known differences in SHR between Inuit and those of European ancestry.

Controlled human wood smoke exposure: oxidative stress, inflammation and microvascular function.

BACKGROUND: Exposure to wood smoke is associated with respiratory symptoms, whereas knowledge on systemic effects is limited. We investigated effects on systemic inflammation, oxidative stress and microvascular function (MVF) after controlled wood smoke exposure. METHODS: In a randomised, double-blinded, cross-over study 20 non-smoking atopic subjects were exposed at rest to 14, 220, or 354 µg/m3 of particles from a well-burning modern wood stove for 3 h in a climate controlled chamber with 2 week intervals. We investigated the level of oxidatively damaged DNA, inflammatory markers and adhesion molecules before and 0, 6 and 20 h after exposure. Six h after exposure we measured MVF non-invasively by digital peripheral artery tonometry following arm ischemia. RESULTS: The MVF score was unaltered after inhalation of clean air (1.58 ± 0.07; mean ± SEM), low (1.51 ± 0.07) or high (1.61 ± 0.09) concentrations of wood smoke particles in atopic subjects, whereas unexposed non-atopic subjects had higher score (1.91 ± 0.09). The level of oxidatively damaged DNA, mRNA of ITGAL, CCL2, TNF, IL6, IL8, HMOX1, and OGG1 and surface marker molecules ICAM1, ITGAL and L-selectin in peripheral blood mononuclear cells were not affected by inhalation of wood smoke particles. CONCLUSIONS: Exposure to wood smoke had no effect on markers of oxidative stress, DNA damage, cell adhesion, cytokines or MVF in atopic subjects.

Effects of wood smoke particles from wood-burning stoves on the respiratory health of atopic humans.

BACKGROUND: There is growing evidence that particulate air pollution derived from wood stoves causes acute inflammation in the respiratory system, increases the incidence of asthma and other allergic diseases, and increases respiratory morbidity and mortality. The objective of this study was to evaluate acute respiratory effects from short-term wood smoke exposure in humans. Twenty non-smoking atopic volunteers with normal lung function and without bronchial responsiveness were monitored during three different experimental exposure sessions, aiming at particle concentrations of about 200 µg/m(3), 400 µg/m(3), and clean air as control exposure. A balanced cross-over design was used and participants were randomly allocated to exposure orders. Particles were generated in a wood-burning facility and added to a full-scale climate chamber where the participants were exposed for 3 hours under controlled environmental conditions. Health effects were evaluated in relation to: peak expiratory flow (PEF), forced expiratory volume in the first second (FEV1), and forced vital capacity (FVC). Furthermore, the effects were assessed in relation to changes in nasal patency and from markers of airway inflammation: fractional exhaled nitric oxide (FENO), exhaled breath condensate (EBC) and nasal lavage (NAL) samples were collected before, and at various intervals after exposure. RESULTS: No statistically significant effect of wood smoke exposure was found for lung function, for FENO, for NAL or for the nasal patency. Limited signs of airway inflammation were found in EBC. CONCLUSION: In conclusion, short term exposure with wood smoke at a concentration normally found in a residential area with a high density of burning wood stoves causes only mild inflammatory response.

Exposure to inhalable dust and endotoxin among Danish livestock farmers: results from the SUS cohort study.

Studies on personal dust and endotoxin concentrations among animal farmers have been either small or limited to a few sectors in their investigations. The present study aimed to provide comparable information on the levels and variability of exposure to personal dust and endotoxin in different types of animal farmers. 507 personal inhalable dust samples were collected from 327 farmers employed in 54 pig, 26 dairy, 3 poultry, and 3 mink farms in Denmark. Measurements in pig and dairy farmers were full-shift and performed during summer and winter, while poultry and mink farmers were monitored during 4 well-defined production stages. The collected samples were measured for dust gravimetrically and analyzed for endotoxin by the Limulus amebocyte lysate assay. Simple statistics and random-effect analysis were used to describe the levels and the variability in measured dust and endotoxin exposure concentrations. Measured inhalable dust levels had an overall geometric mean of 2.5 mg m(-3) (range

Prevalence of Chronic Obstructive Pulmonary Disease and Chronic Bronchitis Among Predominantly Smoking Workers in the Seafood Industry in Greenland.

Introduction: For decades, the prevalence of smoking has been high in Greenland. Even so, the prevalence of chronic obstructive pulmonary disease (COPD), a smoking-related disease, remains largely unexplored. This cross-sectional study aimed to estimate the prevalence of COPD and chronic bronchitis (CB) among Inuit workers in the seafood industry in Greenland. Methods: A total of 355 participants, 254 males and 101 females, met the inclusion criteria. Participants had a mean age of 38 years (standard deviation 13.5; range 17-68 years). COPD was diagnosed based on post-bronchodilator ratio between forced expiratory volume within one second and forced vital capacity (FEV1/FVC) below the lower limit of normal (LLN) according to the Global Lung Function Initiative. Participants completed a questionnaire aiming to diagnose CB. Results: The overall prevalence was 9.9% for COPD; 7.4% for CB. Participants were predominantly smokers; 73.2% active smokers, 91.8% active or former smokers. The prevalence of COPD was high, especially among those under 40 years of age. Both COPD and CB were associated with smoking status. Discussion: This study among Greenlandic seafood workers found that smoking was a risk factor for COPD and CB among Greenlanders of Inuit origin. The high prevalence of COPD and the high prevalence of smoking underlines the importance of further initiatives to reduce smoking in Greenland.

Historical Asbestos Measurements in Denmark-A National Database.

OBJECTIVES: Due to the long lag-time for health outcomes, historical asbestos exposure measurements are valuable to support assessments of associated occupational health effects, and also to assess time trends and effects of preventive measures. METHODS: Different sources of stored data were collated, assessed and refined to create a harmonized database on historical asbestos fibre concentrations measured in specific work tasks and different industries. The final database contains 9236 asbestos measurements from Danish workplaces collected from 1971 to 1997. RESULTS: The geometric mean of asbestos concentrations in different occupations and tasks ranged from 0.003 to 35 fibres cm-3. Highest concentrations were registered during handling of asbestos products in the construction services during the period 1981-1997. Although all the measured asbestos exposures without the use of respiratory equipment by the worker in the period of 1971-1997 exceeded the current 8-h time-weighted average exposure limit of 0.1 fibres cm-3, the majority of samples collected in the earlier period of 1971 to 1980 did not exceed the exposure limit of 2 fibres cm-3, which was in place at the time. All exposure data obtained from 1980 and onwards were found to be one seventh of the mean fibre concentrations in the previous measurement period. The impact of time shows a clear exponentially decreasing trend-line. CONCLUSIONS: Despite limitations in coverage of different occupations and tasks associated with the inventoried historical asbestos measurements, the data are helpful to identify specific work scenarios within an industry, where relatively high asbestos exposure levels may still occur or have occurred from 1971 to 1997.

Serum selenium levels and asthma among seafood processing workers in Greenland.

Selenium levels in the Inuit population of Greenland have been declining during the last decades. The association between Selenium and asthma has been investigated previously, but with conflicting results. The objective was to measure human serum Se (s-Se) in Greenlandic seafood processing workers, to compare with levels recorded in previous decades and to establish if s-Se is associated with asthma or lung function. Data, including questionnaire answers, spirometry, skin-prick test and s-Se from 324 seafood processing workers in Greenland were collected during 2016-2017. Mean s-Se values were compared by t-test and one-way ANOVA. Associations between s-Se and asthma, symptoms from the lower airways at work and lung function were assessed using linear regression. The mean s-Se was 96.2 µg/L. S-Se was higher among non-smokers and workers living in settlements. Workers with asthma did not have s-Se levels significantly different from those of non-asthmatics. We found a positive association between s-Se levels and FEV1 values. Selenium levels appear to continue declining in Greenland, presumably because of a more Westernised lifestyle. The health effects of declining Selenium levels remain unclear. We did not establish an association between s-Se and asthma, but we did record a positive association between s-Se and FEV1.

The Effect of Seasonal Priming on Specific Inhalation Challenges With Birch and Grass Allergen Among Persons With Allergic Rhinitis.

Objectives: Allergic diseases are prevalent in the working population, and work-related airborne pollen exposure might be substantial, especially among outdoor workers, resulting in work-exacerbated effects. Seasonal exposure to pollen may induce a priming effect on the allergic bronchial response resulting in exaggerated effects at the end of the natural pollen season. This was previously observed among people with asthma but may also be of importance for persons with allergic rhinitis. In this study, we examined the effect of seasonal priming on bronchial responsiveness among young adults with allergic rhinitis and no or mild asthma. In addition, we explored the association between the baseline characteristics of participants and the severity of bronchoconstriction. Finally, we evaluated the application of a novel non-linear regression model to the log-dose-response curves. Material and methods: In a crossover design, 36 participants underwent specific inhalation challenges (SICs) with either grass or birch allergen outside and at the end of the pollen season. The differences in bronchial response were evaluated by comparing the dose-response profiles and PD20 estimates derived by applying a non-linear regression model. Results: The results showed that 12 of the 19 grass pollen-exposed participants had a lower PD20 at the end of the season compared with the outside season. For birch, this was true for nine out of the 17 participants. However, no statistically significant effects of the seasonal pollen exposure were found on neither the shape nor the magnitude of the modeled dose-response curves for either birch allergen, p = 0.77, or grass allergen, p = 0.45. The model depicted a good fit for the data. Among the baseline characteristics, only the size of the skin prick test for grass allergen was associated with PD20. Conclusion: This study does not support a priming effect of pollen exposure on the bronchial response from the natural seasonal exposure levels of grass or birch allergens among young adults with allergic rhinitis.