The effectiveness of removal from exposure and reduction of exposure for managing occupational asthma: Summary of an updated Cochrane systematic review.

BACKGROUND: The objective was to update the 2011 Cochrane systematic review on the effectiveness of workplace interventions for the treatment of occupational asthma. METHODS: A systematic review was conducted with the selection of articles and reports through 2019. The quality of extracted data was evaluated, and meta-analyses were conducted using techniques recommended by the Cochrane Handbook for Systematic Reviews of Interventions. RESULTS: Data were extracted from 26 nonrandomized controlled before-and-after studies. The mean number of participants per study was 62 and the mean follow-up time was 4.5 years. Compared with continued exposure, removal from exposure had an increased likelihood of improved symptoms and change in spirometry. Reduction of exposure also had more favorable results for symptom improvement than continued exposure, but no difference for change in spirometry. Comparing exposure removal to reduction revealed an advantage for removal with both symptom improvement and change in spirometry for the larger group of patients exposed to low-molecular-weight agents. Also, the risk of unemployment was greater for exposure removal versus reduction. CONCLUSIONS: Exposure removal and reduction had better outcomes than continued exposure. Removal from exposure was more likely to improve symptoms and spirometry than reduction among patients exposed to low-molecular-weight agents. The potential benefits associated with exposure removal versus reduction need to be weighed against the potential for unemployment that is more likely with removal from exposure. The findings are based on data graded as very low quality, and additional studies are needed to generate higher quality data.

Aerotoxic syndrome, discussion of possible diagnostic criteria.

Introduction: The term aerotoxic syndrome (ATS) was proposed 20 years ago to describe a constellation of symptoms reported by pilots and cabin crew following exposure to hydraulic fluids, engine oil, and pyrolysis products during flight. Hydraulic fluids and engine oil contain a large number of potentially toxic chemicals, including various organophosphate compounds (OPCs). However, ATS is not yet recognised as a valid diagnosis in aviation or general medicine, because the incidence and aetiology continues to be debated.Discussion: Early studies report findings from symptom surveys or cognitive assessments of small samples of self-selected aircrew, but objective measures of exposure were lacking. Over the last decade, researchers have used more sophisticated techniques to measure exposure, such as on board monitoring studies and biomarkers of exposure (e.g., reduced levels of serum butyrylcholinesterases [BChE]) and more sophisticated techniques to detect nervous system injuries such as fMRI and autoantibody testing. Consideration has also been given to inter-individual differences in the ability to metabolise certain chemical compounds as a result of genetic polymorphisms and exclusion of other potential causes of ill health.Conclusions: We discuss factors which suggest a diagnosis of probable ATS; recommend an assessment protocol which incorporates the aforementioned techniques; and propose diagnostic criteria for probable ATS, based on our previously reported findings in aircrew and the results of recent studies.

Workplace interventions for treatment of occupational asthma.

BACKGROUND: The impact of workplace interventions on the outcome of occupational asthma is not well understood. OBJECTIVES: To evaluate the effectiveness of workplace interventions on occupational asthma. SEARCH METHODS: We searched the Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE (PubMed); EMBASE(Ovid); NIOSHTIC-2; and CISILO (CCOHS) up to July 31, 2019. SELECTION CRITERIA: We included all eligible randomized controlled trials, controlled before and after studies and interrupted time-series of workplace interventions for occupational asthma. DATA COLLECTION AND ANALYSIS: Two authors independently assessed study eligibility and risk of bias, and extracted data. MAIN RESULTS: We included 26 non-randomized controlled before and after studies with 1,695 participants that reported on three comparisons: complete removal from exposure and reduced exposure compared to continued exposure, and complete removal from exposure compared to reduced exposure. Reduction of exposure was achieved by limiting use of the agent, improving ventilation, or using protective equipment in the same job; by changing to another job with intermittent exposure; or by implementing education programs. For continued exposure, 56 per 1000 workers reported absence of symptoms at follow-up, the decrease in forced expiratory volume in one second as a percentage of a reference value (FEV1 %) was 5.4% during follow-up, and the standardized change in non-specific bronchial hyperreactivity (NSBH) was -0.18.In 18 studies, authors compared removal from exposure to continued exposure. Removal may increase the likelihood of reporting absence of asthma symptoms, with risk ratio (RR) 4.80 (95% confidence interval (CI) 1.67 to 13.86), and it may improve asthma symptoms, with RR 2.47 (95% CI 1.26 to 4.84), compared to continued exposure. Change in FEV1 % may be better with removal from exposure, with a mean difference (MD) of 4.23 % (95% CI 1.14 to 7.31) compared to continued exposure. NSBH may improve with removal from exposure, with standardized mean difference (SMD) 0.43 (95% CI 0.03 to 0.82).In seven studies, authors compared reduction of exposure to continued exposure. Reduction of exposure may increase the likelihood of reporting absence of symptoms, with RR 2.65 (95% CI 1.24 to 5.68). There may be no considerable difference in FEV1 % between reduction and continued exposure, with MD 2.76 % (95% CI -1.53 to 7.04) . No studies reported or enabled calculation of change in NSBH.In ten studies, authors compared removal from exposure to reduction of exposure. Following removal from exposure there may be no increase in the likelihood of reporting absence of symptoms, with RR 6.05 (95% CI 0.86 to 42.34), and improvement in symptoms, with RR 1.11 (95% CI 0.84 to 1.47), as well as no considerable change in FEV1 %, with MD 2.58 % (95% CI -3.02 to 8.17). However, with all three outcomes, there may be improved results for removal from exposure in the subset of patients exposed to low molecular weight agents. No studies reported or enabled calculation of change in NSBH.In two studies, authors reported that the risk of unemployment after removal from exposure may increase compared with reduction of exposure, with RR 14.28 (95% CI 2.06 to 99.16). Four studies reported a decrease in income of 20% to 50% after removal from exposure.The quality of the evidence is very low for all outcomes. AUTHORS' CONCLUSIONS: Both removal from exposure and reduction of exposure may improve asthma symptoms compared with continued exposure. Removal from exposure, but not reduction of exposure, may improve lung function compared to continued exposure. When we compared removal from exposure directly to reduction of exposure, the former may improve symptoms and lung function more among patients exposed to low molecular weight agents. Removal from exposure may also increase the risk of unemployment. Care providers should balance the potential clinical benefits of removal from exposure or reduction of exposure with potential detrimental effects of unemployment. Additional high-quality studies are needed to evaluate the effectiveness of workplace interventions for occupational asthma.

Workplace interventions for treatment of occupational asthma.

BACKGROUND: The impact of workplace interventions on the outcome of occupational asthma is not well-understood. OBJECTIVES: To evaluate the effectiveness of workplace interventions on the outcome of occupational asthma. SEARCH STRATEGY: We searched the Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; EMBASE; NIOSHTIC-2; CISDOC and HSELINE up to February 2011. SELECTION CRITERIA: Randomised controlled trials, controlled before and after studies and interrupted time series of workplace interventions for occupational asthma. DATA COLLECTION AND ANALYSIS: Two authors independently assessed study eligibility and trial quality, and extracted data. MAIN RESULTS: We included 21 controlled before and after studies with 1447 participants that reported on 29 comparisons.In 15 studies, removal from exposure was compared with continued exposure. Removal increased the likelihood of reporting absence of symptoms (risk ratio (RR) 21.42, 95% confidence interval (CI) 7.20 to 63.77), improved forced expiratory volume (FEV1 %) (mean difference (MD) 5.52 percentage points, 95% CI 2.99 to 8.06) and decreased non-specific bronchial hyper-reactivity (standardised mean difference (SMD) 0.67, 95% CI 0.13 to 1.21).In six studies, reduction of exposure was compared with continued exposure. Reduction increased the likelihood of reporting absence of symptoms (RR 5.35, 95% CI 1.40 to 20.48) but did not affect FEV1 % (MD 1.18 percentage points, 95% CI -2.96 to 5.32).In eight studies, removal from exposure was compared with reduction of exposure. Removal increased the likelihood of reporting absence of symptoms (RR 39.16, 95% CI 7.21 to 212.83) but did not affect FEV1 % (MD 1.16 percentage points, 95% CI -7.51 to 9.84).Two studies reported that the risk of unemployment after removal from exposure was increased compared with reduction of exposure (RR 14.3, 95% CI 2.06 to 99.16). Three studies reported loss of income of about 25% after removal from exposure.Overall the quality of the evidence was very low. AUTHORS' CONCLUSIONS: There is very low-quality evidence that removal from exposure improves asthma symptoms and lung function compared with continued exposure.Reducing exposure also improves symptoms, but seems not as effective as complete removal.However, removal from exposure is associated with an increased risk of unemployment, whereas reduction of exposure is not. The clinical benefit of removal from exposure or exposure reduction should be balanced against the increased risk of unemployment. We need better studies to identify which interventions intended to reduce exposure give most benefit.