Paul K. Henneberger

An Official American Thoracic Society Statement: Work-Exacerbated Asthma

RATIONALE Occupational exposures can contribute to the exacerbation as well as the onset of asthma. However, work-exacerbated asthma (WEA) has received less attention than occupational asthma (OA) that is caused by work. OBJECTIVES The purpose of this Statement is to summarize current knowledge about the descriptive epidemiology, clinical characteristics, and management and treatment of WEA; propose a case definition for WEA; and discuss needs for prevention and research. METHODS Information about WEA was identified primarily by systematic searches of the medical literature. Statements about prevention and research needs were reached by consensus. MEASUREMENTS AND MAIN RESULTS WEA is defined as the worsening of asthma due to conditions at work. WEA is common, with a median prevalence of 21.5% among adults with asthma. Different types of agents or conditions at work may exacerbate asthma. WEA cases with persistent work-related symptoms can have clinical characteristics (level of severity, medication needs) and adverse socioeconomic outcomes (unemployment, reduction in income) similar to those of OA cases. Compared with adults with asthma unrelated to work, WEA cases report more days with symptoms, seek more medical care, and have a lower quality of life. WEA should be considered in any patient with asthma that is getting worse or who has work-related symptoms. Management of WEA should focus on reducing work exposures and optimizing standard medical management, with a change in jobs only if these measures are not successful. CONCLUSIONS WEA is a common and underrecognized adverse outcome resulting from conditions at work. Additional research is needed to improve the understanding of the risk factors for, and mechanisms and outcomes of, WEA, and to inform and evaluate preventive interventions.

Guidelines for the management of work-related asthma

Work-related asthma, which includes occupational asthma and work-aggravated asthma, has become one of the most prevalent occupational lung diseases. These guidelines aim to upgrade occupational health standards, contribute importantly to transnational legal harmonisation and reduce the high socio-economic burden caused by this disorder. A systematic literature search related to five key questions was performed: diagnostics; risk factors; outcome of management options; medical screening and surveillance; controlling exposure for primary prevention. Each of the 1,329 retrieved papers was reviewed by two experts, followed by Scottish Intercollegiate Guidelines Network grading, and formulation of statements graded according to the Royal College of General Practitioners’ three-star system. Recommendations were made on the basis of the evidence-based statements, which comprise the following major evidence-based strategic points. 1) A comprehensive diagnostic approach considering the individual specific aspects is recommended. 2) Early recognition and diagnosis is necessary for timely and appropriate preventative measures. 3) A stratified medical screening strategy and surveillance programme should be applied to at-risk workers. 4) Whenever possible, removing exposure to the causative agent should be achieved, as it leads to the best health outcome. If this is not possible, reduction is the second best option, whereas respirators are of limited value. 5) Exposure elimination should be the preferred primary prevention approach.

Industries in the United States with Airborne Beryllium Exposure and Estimates of the Number of Current Workers Potentially Exposed

Estimates of the number of workers in the United States occupationally exposed to beryllium were published in the 1970s and 1980s and ranged from 21,200 to 800,000. We obtained information from several sources to identify specific industries with beryllium exposure and to estimate the number of current workers potentially exposed to beryllium. We spoke with representatives from the primary beryllium industry and government agencies about the number of exposed workers in their facilities. To identify industries in the private sector but outside the primary industry, we used data from the Integrated Management Information System (IMIS), which is managed by the Occupational Safety and Health Administration, and the Health Hazard Evaluation program of the National Institute for Occupational Safety and Health. We used IMIS data from OSHA inspections with a previously developed algorithm to estimate the number of potentially exposed workers in nonprimary industries. Workers potentially exposed to beryllium included 1500 current employees in the primary beryllium industry and 26,500 individuals currently working for the Department of Energy or the Department of Defense. We identified 108 four-digit Standard Industrial Classification (SIC) categories in which at least one measurement of airborne beryllium was ≥ 0.1 μ g/m3. Based on the subset of 94 SIC categories with beryllium ≥ 0.1 μ g/m3, we estimated 26,400 to 106,000 workers may be exposed in the private sector (outside the primary industry). In total, there are as many as 134,000 current workers in government and private industry potentially exposed to beryllium in the United States. We recommend that the results of this study be used to target at-risk audiences for hazard communications intended to prevent beryllium sensitization and chronic beryllium disease.

Pesticide use and adult-onset asthma among male farmers in the Agricultural Health Study

Although specific pesticides have been associated with wheeze in farmers, little is known about pesticides and asthma. Data from 19,704 male farmers in the Agricultural Health Study were used to evaluate lifetime use of 48 pesticides and prevalent adult-onset asthma, defined as doctor-diagnosed asthma after the age of 20 yrs. Asthma cases were categorised as allergic (n = 127) and nonallergic (n = 314) based on their history of eczema or hay fever. Polytomous logistic regression, controlling for age, state, smoking and body mass, was used to assess pesticide associations. High pesticide exposure events were associated with a doubling of both allergic and nonallergic asthma. For ever-use, 12 individual pesticides were associated with allergic asthma and four with nonallergic asthma. For allergic asthma, coumaphos (OR 2.34; 95% CI 1.49–3.70), heptachlor (OR 2.01; 95% CI 1.30–3.11), parathion (OR 2.05; 95% CI 1.21–3.46), 80/20 mix (carbon tetrachloride/carbon disulfide) (OR 2.15; 95% CI 1.23–3.76) and ethylene dibromide (OR 2.07; 95% CI 1.02–4.20) all showed ORs of >2.0 and significant exposure–response trends. For nonallergic asthma, DDT (dichlorodiphenyltrichloroethane) showed the strongest association (OR 1.41; 95% CI 1.09–1.84), but with little evidence of increasing asthma with increasing use. Current animal handling and farm activities did not confound these results. There was little evidence that allergy alone was driving these associations. In conclusion, pesticides may be an overlooked contributor to asthma risk among farmers.

Induction of Asthma and the Environment: What We Know and Need to Know

The prevalence of asthma has increased dramatically over the last 25 years in the United States and in other nations as a result of ill-defined changes in living conditions in modern society. On 18 and 19 October 2004 the U.S. Environmental Protection Agency and the National Institute of Environmental Health Sciences sponsored the workshop “Environmental Influences on the Induction and Incidence of Asthma” to review current scientific evidence with respect to factors that may contribute to the induction of asthma. Participants addressed two broad questions: a) What does the science suggest that regulatory and public health agencies could do now to reduce the incidence of asthma? and b) What research is needed to improve our understanding of the factors that contribute to the induction of asthma and our ability to manage this problem? In this article (one of four articles resulting from the workshop), we briefly characterize asthma and its public health and economic impacts, and intervention strategies that have been successfully used to prevent induction of asthma in the workplace. We conclude with the findings of seven working groups that focus on ambient air, indoor pollutants (biologics), occupational exposures, early life stages, older adults, intrinsic susceptibility, and lifestyle. These groups found strong scientific support for public health efforts to limit in utero and postnatal exposure to cigarette smoke. However, with respect to other potential types of interventions, participants noted many scientific questions, which are summarized in this article. Research to address these questions could have a significant public health and economic impact that would be well worth the investment.

A descriptive study of work aggravated asthma

Background and Aims: Work related asthma (WRA) is one of the most frequently reported occupational lung diseases in a number of industrialised countries. A better understanding of work aggravated asthma (WAA), as well as work related new onset asthma (NOA), is needed to aid in prevention efforts. Methods: WAA and NOA in the United States were compared using cases reported to the National Institute for Occupational Safety and Health (NIOSH) from four state Sentinel Event Notification Systems for Occupational Risks (SENSOR) surveillance programmes for 1993–95. Results: A total of 210 WAA cases and 891 NOA cases were reported. WAA cases reported mineral and inorganic dusts as the most common exposure agent, as opposed to NOA cases, in which diisocyanates were reported most frequently. A similar percentage of WAA and NOA cases still experienced breathing problems at the time of the interview or had visited a hospital or emergency room for work related breathing problems. NOA cases were twice as likely to have applied for workers’ compensation compared with WAA cases. However, among those who had applied for worker compensation, approximately three-fourths of both WAA and NOA cases had received awards. The services and manufacturing industrial categories together accounted for the majority of both WAA (62%) and NOA (75%) cases. The risk of WAA, measured by average annual rate, was clearly the highest in the public administration (14.2 cases/105) industrial category, while the risk of NOA was increased in both the manufacturing (3.2 cases/105) and public administration (2.9 cases/105) categories. Conclusions: WAA cases reported many of the same adverse consequences as NOA cases. Certain industries were identified as potential targets for prevention efforts based on either the number of cases or the risk of WAA and NOA.

Mortality in the agricultural health study, 1993-2007.

Comparing agricultural cohorts with the general population is challenging because the general healthiness of farmers may mask potential adverse health effects of farming. Using data from the Agricultural Health Study, a cohort of 89,656 pesticide applicators and their spouses (N = 89, 656) in North Carolina and Iowa, the authors computed standardized mortality ratios (SMRs) comparing deaths from time of the enrollment (1993-1997) through 2007 to state-specific rates. To compensate for the cohorts overall healthiness, relative SMRs were estimated by calculating the SMR for each cause relative to the SMR for all other causes. In 1,198,129 person-years of follow-up, 6,419 deaths were observed. The all-cause mortality rate was less than expected (SMR(applicators) = 0.54, 95% confidence interval (CI): 0.52, 0.55; SMR(spouses) = 0.52, 95% CI: 0.50, 0.55). SMRs for all cancers, heart disease, and diabetes were significantly below 1.0. In contrast, applicators experienced elevated numbers of machine-related deaths (SMR = 4.15, 95% CI: 3.18, 5.31), motor vehicle nontraffic accidents (SMR = 2.80, 95% CI: 1.81, 4.14), and collisions with objects (SMR = 2.12, 95% CI: 1.25, 3.34). In the relative SMR analysis for applicators, the relative mortality ratio was elevated for lymphohematopoietic cancers, melanoma, and digestive system, prostate, kidney, and brain cancers. Among spouses, relative SMRs exceeded 1.0 for lymphohematopoietic cancers and malignancies of the digestive system, brain, breast, and ovary. Unintentional fatal injuries remain an important risk for farmers; mortality ratios from several cancers were elevated relative to other causes.

Primary prevention: exposure reduction, skin exposure and respiratory protection

Interventions for the primary prevention of occupational asthma have been reported in the medical literature, understanding the effectiveness of these efforts could help future interventions. The aim of our study was to evaluate the existing knowledge regarding the impact of controlling work exposure on the prevention of occupational asthma. We conducted systematic literature searches through April 2010 to examine if control of workplace exposures is effective for primary prevention of sensitisation and occupational asthma. The literature search for primary prevention of occupational asthma yielded 29 studies. Assessment of the available information led to the following conclusions and recommendations concerning primary prevention of occupational asthma. Exposure elimination is the strongest and preferred primary preventive approach to reduce the burden of occupational asthma. If elimination is not possible, exposure reduction is the second best option for primary prevention of occupational asthma. The evidence for the effectiveness of respirators in preventing occupational asthma is limited, and other options higher in the list of controls for occupational exposures, notably eliminating or minimising exposures at the source or in the environment, should be used preferentially. There is strong evidence to recommend not using powdered allergen-rich natural rubber latex gloves. There is weak evidence that suggests workers should minimise skin exposure to asthma-inducing agents.

Management of occupational asthma: cessation or reduction of exposure? A systematic review of available evidence

Reduction of exposure to sensitising agents causing occupational asthma has been proposed as an alternative to total avoidance in order to minimise the adverse socio-economic impact of the condition. The aim of this systematic review was to compare the effects of these two management options on asthma and socio-economic outcomes. A bibliographic search was conducted to identify studies examining the outcome of workers with occupational asthma after reduction or cessation of exposure to the causal agent. The changes in asthma symptoms and nonspecific bronchial hyperresponsiveness after reduction or cessation of exposure were described in nine and five studies, respectively. The meta-analysis of pooled data showed that a reduction of exposure was associated with a lower likelihood of improvement (OR 0.16, 95% CI 0.03–0.91) and recovery (OR 0.30, 95% CI 0.11–0.84) of asthma symptoms and a higher risk of worsening of the symptoms (OR 10.23, 95% CI 2.97–35.28) and nonspecific bronchial hyperresponsiveness (OR 5.65, 95% CI 1.11–28.82), compared with complete avoidance of exposure. This systematic review indicates that reduction of exposure cannot be routinely recommended as an alternative to cessation of exposure in the management of occupational asthma. However, further investigations are required before drawing evidence-based conclusions on the cost-effectiveness of this approach.

Work-exacerbated asthma

Purpose of review To summarize recent findings on work-exacerbated asthma, based on medical literature published during 2005 and the first 10 months of 2006. Recent findings Although prevalence estimates varied considerably among six recent epidemiologic studies, collectively they contribute to the conclusion that work-exacerbated asthma is common. Median work-exacerbated asthma prevalence estimates were 18% of adults with asthma, 25% of working adults with asthma and 45% of all work-related asthma cases. Work-exacerbated asthma can result from a variety of occupational triggers, including physical factors (e.g. extreme temperatures, exercise), behavioral states (e.g. strong emotions, stress), odors (e.g. perfume), general irritants and dust, and second-hand cigarette smoke. Work-exacerbated asthma cases have many of the same demographic and clinical traits as other adults with asthma and occupational asthma cases, although some differences have been reported. Recent review articles have offered some recommendations on the management of work-exacerbated asthma, but more comprehensive advice is anticipated from a professional medical society in the next few years. Summary Epidemiologic studies indicate that work-exacerbated asthma is common. Researchers have started to pay attention to work-exacerbated asthma, but more studies are needed on all aspects of this condition in order to improve diagnosis, management and prevention.