Browsing by Author "Jeebhay, Mohamed Fareed"

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    Open Access
    A prospective cohort study on ambient air pollution, airborne pollen (and fungal spores) and respiratory morbidities including childhood asthma in adolescents from the Western Cape Province
    (2018) Olaniyan, Toyib Adedamola; Dalvie, Mohamed Aqiel; Jeebhay, Mohamed Fareed; Röösli, Martin
    Background: The epidemiological studies investigating environmental risk factors associated with asthma among children living in informal settlements are scant as are studies on the independent and co-pollutant effect of short- and long-term exposures to ambient air pollutants as well as fungal spores on asthma-associated outcomes. This study systematically investigated these factors among schoolchildren residing in informal settlements in the Western Cape province of South Africa. Methods: A cohort study of grade-4 schoolchildren (n=590) recruited from six primary schools in four informal settlements was conducted over 12 months. In addition, a panel study, investigated the children for 2 consecutive school weeks in both summer and winter. Spirometry and fractional-exhaled nitric oxide (FeNO) measurements were conducted during the school day, while the International Study on Asthma and Allergy in Children (ISAAC) standardised questionnaire was administered to the parent or guardian at the child’s home at baseline and follow-up. The presence of atopy was determined based on a positive Phadiatop test on sera. In the cohort study, annual NO2 and PM2.5 levels were computed for each child’s address using a land-use regression model. Daily PM10 levels obtained from a stationary monitor near two of the study areas were used for the panel study. Airborne pollen and fungal spore measurements were obtained directly from a stationary monitor placed in each study area. Results: The prevalence of doctor-diagnosed asthma was 3.4% and only half of them were on asthma treatment. The prevalence of wheezing in the past 12 months (12.9%), airway obstruction (17.6%) and airway inflammation (10.2%) was much higher. The presence of damp conditions, visible mould growth, passive smoking as well as paraffin-use for cooking and heating were significant indoor risk factors for asthma. The estimated annual average NO2 level of 16.6 µg/m3 was below the WHO annual exposure standards, however more than a third of children were exposed to annual PM2.5 levels above the 10 µg/m3 WHO standard and the allergic symptom threshold level of 100 spores/m3 for Alternaria spores. In the panel study, daily exposure of schoolchildren to Alternaria and Cladosporium spores independently decreased FEV1 (-27.56 ml, 95% CI: -50.60 to -4.51 ml per 10 spores/m3 increase in Alternaria; and -86.19ml, 95% CI: -131.69 to -40.70 ml per 50 spores/m3 increase in Cladosporium respectively) from lag day-0 to lag day-5, especially in the winter monitoring period. In the cohort study, an interquartile range increase of 14.2 µg/m3 in annual NO2 was associated with an risk of new onset ocular-nasal symptoms (adjusted odds ratio – aOR: 1.63, 95% CI: 1.01 – 2.60), wheezing (aOR: 3.57, 95% CI: 1.18 – 10.92), more than two or more asthma symptom score (aOR: 1.71, 95% CI: 1.02 – 2.86), and airway inflammation defined as FeNO > 35ppb (aOR: 3.10, 95% CI: 1.10 – 8.71), independent of PM2.5 exposures. In addition, an interquartile increase of 83.1 spores/m3 in 24-hour annual Alternaria spore levels was associated with an increased risk of airway inflammation incidence and having a ≥ 10% increase in FeNO at follow-up both in the single-pollutant model and two-pollutant model. Conclusion: This study demonstrated a large proportion of undiagnosed and untreated asthma in schoolchildren living in informal settlements, with both indoor and outdoor mould exposures playing an important role in addition to ambient chemical pollutants. The incidence of new onset asthma symptoms and airway inflammation associated with NO2 at levels below the WHO Air Quality Standards raises the issue of the adequacy of these standards in protecting respiratory health. Raised long-term levels of airborne Alternaria spores contributing to increased airway inflammation is likely to form the basis for the increased risk of acute symptoms and airway effects observed in association with exposure peaks.
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    Open Access
    Determinants of occupational allergic respiratory disease and asthma in spice mill workers
    (2010) Van der Walt, Anita; Jeebhay, Mohamed Fareed
    The aim of this study was to determine the prevalence of occupational allergy and asthma associated with airborne spice and to determine the host and environmental risk factors associated with allergic respiratory disease among spice mill workers. A cross-sectional epidemiological study of 150 currently employed workers in a spice mill was conducted. Environmental exposure assessment entailed the collection of 62 full-shift airborne personal samples on randomly selected individuals employed in various departments of the spice mill using the NIOSH occupational exposure sampling strategy manual. The samples were analysed for inhalable particulate mass, specific spice dust allergens (garlic) and endotoxin using ELISA inhibition (antibodies from sensitised subjects) and chromogenic LAL assays.
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    Predictors of obstructive lung disease among seafood processing workers along the west coast of the Western Cape of South Africa
    (2007) Adams, Shahieda; Jeebhay, Mohamed Fareed
    Introduction: This study examined the patterns and the prevalence of obstructive lung disease (asthma and COPD) and associated risk factors (age, gender, atopy, smoking history, allergic history, previous history of lung disease, occupational exposures, seafood intake) in a working population of seafood processing workers along the West coast of the Western Cape of South Africa. Materials and method: A cross-sectional study was conducted 643 currently employed workers in two fish processing plants working fish canning and fishmeal processing. A modified version of the European Community Respiratory Health Survey (ECRHS) questionnaire was used. Skin prick tests (SPT) used extracts of common airborne allergen. Lung function spirometry and methacholine challenge tests (tidal breathing method) conducted using Vitallograph S-model bellows volume-time spirometers according to ATS guidelines. Serum omega-3 and omega-6 fatty acid levels also analysed to examine the association between dietary fatty acids and asthma outcomes. Multivariate regression models were developed for asthma outcomes after adjusting for age, gender, sex and atopic status whilst the models were adjusted for age, gender and smoking history for COPD outcomes.
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    Predictors of occupational sensitisation to grain dust allergens and changes in lung function among grain mill workers in Cape Town
    (1998) Jeebhay, Mohamed Fareed; Ehrlich, Rodney I
    Occupationally-related airway diseases, including asthma and chronic obstructive lung disease, have emerged as having substantial public health importance. The aim of this study was to identify the predictors of occupational sensitisation to grain dust allergens and changes in lung function among grain mill workers in Cape Town. There were two major objectives of the study. Firstly, to determine which of the following factors determine the distribution of serum ECP (eosinophilic cationic protein): age, gender, grain dust exposure, smoking status, atopy and sensitisation to workplace allergens. Secondly, to investigate the risk factors associated with the following outcomes: i) sensitisation to occupational allergens; ii) diagnosis of occupational asthma; iii) diagnosis of chronic obstructive airways disease; and iv) longitudinal changes in lung function. The risk factors studied included age, gender, smoking habits, occupational exposure, lung function status on baseline survey (1989), and allergic sensitisation assessed at follow up (1996). The methods employed involved a repeat measures cross-sectional design including a cohort followed up at different points over a seven year period. Survey instruments included a questionnaire, spirometry and allergy tests (phadiotop, RAST for wheat, rye, Lepidoglyphus destructor, Tyrophagus putrescentiae and Sitophilus granarius). The results indicated an association of grain dust with pulmonary function and allergic sensitisation to grain dust constituents. After adjusting for known confounders such as age, gender and smoking, significant associations were found between employment duration and both decrements in lung function and sensitisation to wheat grain. A decrement of 278 ml in FEY 1 and 328 ml in FYC was associated with occupational sensitisation to wheat (and rye). Increasing employment duration resulted in annual decrements of 18.3 ml in FEY1 and 23 ml in FYC for every year employed. The odds for developing occupational asthma was only mildly elevated (OR=l.35) with increasing employment duration. Age, however, was found to be protective (OR=0.85). Although we were unable to demonstrate a relationship between across-week changes in lung function, at inception, and rapid longitudinal lung function decline, our findings suggested that longitudinal change was related to the degree of airway obstruction at inception. Sensitisation to grain dust allergens was also found to be an independent predictor for FEY 1 and FYC. The prevalence of sensitisation was the highest for wheat (26.4%), followed by Tyrophagus putrescentiae (22.6%), rye (21.7%), Lepidoglyphus destructor (15.1 %) and Sitophilus granarius (15.1 %). Sensitisation to wheat was highly correlated with sensitisation to rye (r = 0.92) and so were Lepidoglyphus destructor and Tyrophagus putrescentiae (r = 0.85). Although a large proportion of the workforce ( 41.5 % ) were sensitised to occupational allergens, the prevalence of respiratory symptoms was between 15.6% and 23.9%. There were 16.7% of workers with health outcomes which fulfilled our criteria for occupational asthma. Atopic workers in our study had at least a nine-fold increased odds of becoming sensitised to grain dust allergens (OR: 8.9-74.7) and a two-fold increased odds of developing occupational asthma (OR= 1.9-84.9). Furthermore, the study found that smokers had a twofold increased odds of becoming atopic, thereby placing them at greater risk of developing respiratory health problems. The mean ECP in this population was 15.4 ug/1 (SD:2.5). Although 45.3% of the workers were atopic, it was not found to be predictor of elevated ECP levels. We were however able to demonstrate a significant association between ECP and sensitisation to grain allergens. Workers sensitised to wheat (positive RAST) had, on average, 1. 78 ug/1 higher ECP levels. The odds of having an elevated ECP (> 15 ug/1) increased by 2.9 for workers sensitised to wheat grain. In conclusion, the results of the study indicate that selection effects are in operation, demonstrating the health worker effect. The findings also suggest that across week reactions may be less sensitive than the across shift changes in predicting rapid longitudinal decline in lung function. While we were able to characterise the distribution of ECP according to exposure, we were however unable to define the temporal relationship between elevated between exposures, ECP and lung function outcomes due to limitations of the study design.
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    Risk factors for work-related asthma in health workers with exposure to diverse cleaning agents in two African health care settings
    (2019) Mwanga, Hussein Hassan; Jeebhay, Mohamed Fareed; Baatjies, Roslynn
    Background: Health workers (HWs) are exposed to a wide range of chemicals used for cleaning and disinfection. This has been largely attributed to the ever-increasing demand for effective cleaning and disinfection in hospital settings in an effort to prevent healthcare associated infections. Over the last two decades, there has been increasing evidence linking cleaning agents to adverse work-related health effects such as rhinitis, asthma and contact dermatitis. There is however little information on the specific cleaning agents and tasks associated with various asthma-related outcomes. Furthermore, limited information exists regarding exposure-response relationships between the frequency of exposure to specific cleaning agents and asthma-related outcomes. This study investigated the prevalence and risk factors for work-related asthma (WRA) among HWs exposed to diverse cleaning agents in two academic tertiary public hospitals in southern Africa - South Africa and Tanzania. Methods: A cross-sectional study of 699 HWs was conducted. Exposure assessment included systematic workplace observations, environmental sampling for aldehydes (orthophthalaldehyde-OPA, glutaraldehyde and formaldehyde) and urine biomonitoring for chlorhexidine. Environmental sampling for aldehydes was conducted more extensively in the South African hospital (SAH). A pilot sampling in the Tanzanian hospital (TAH) revealed very low detectable levels of OPA and glutaraldehyde and as a result extensive measurements were not done. In the SAH, a total of 269 full-shift passive personal samples were collected from 164 HWs randomly selected from 17 different clinical departments. Passive sampling used TraceAir® AT580 monitors (Assay Technology, Livermore, CA). Biomonitoring for chlorhexidine was only conducted in the SAH since none of the HWs in the TAH used chlorhexidine. For the health outcome assessment, a total of 697 HWs completed interviews using the ECRHS questionnaire adapted for occupational contexts, which contained in-depth information on asthma, as well as detailed information on tasks and chemicals used during the course of their work. Sera was successfully collected from 682 HWs and analysed for specific immunoglobulin E (sIgE) antibody reactivity to common aero-allergens (Phadiatop) and specific occupational allergens (NRL - Hevea brasiliensis (Hev b5, Hev b6.02), chlorhexidine and OPA). Methacholine challenge tests (MCT) were performed on all South African HWs (n=318), based on standard inclusion criteria. Spirometry, accompanied by a post-bronchodilator (post-BD) test was conducted on all Tanzanian HWs (n=329) and a small proportion (n=25) of South African HWs where MCT was contraindicated. All HWs from both hospitals (n=654) underwent fractional exhaled nitric oxide (FeNO) testing during the working day prior to spirometry. Results: The prevalence of current asthma was 10% (atopic asthma 6%, non-atopic asthma 4%), while 2% had WRA. The prevalence of atopy was 43%, with 4% of workers being sensitised to OPA, 2% to NRL and only 1% to chlorhexidine. Environmental sampling demonstrated that OPA was detectable in 6 (2%) samples, all samples (Geometric mean (GM) = 0.010 ppm) being higher than the ACGIH exposure limit (0.0001 ppm). Workers with detectable OPA were found to have a longer duration of OPA use (OR = 1.28; 95% CI: 1.10 – 1.50). Formaldehyde was detectable in 103 (38%) samples (GM = 0.005 ppm), with 1% of samples having levels higher than the NIOSH TWA exposure limit (0.016 ppm). Asthmarelated outcomes (increasing asthma symptom score and FeNO) demonstrated consistent positive associations with certain medical instrument cleaning agents (OPA, QACs and enzymatic cleaners) and tasks (pre-cleaning of medical instruments, changing sterilisation solutions and manual disinfection of medical instruments) as well as certain patient care activities (disinfection prior to procedures, cleaning/disinfecting wounds, application of wound dressing, usage of adhesives and adhesive removing solvents). A particularly pronounced dose-response relationship was observed between work-related ocular-nasal symptoms and medical instrument cleaning agents (OPA, glutaraldehdye, QACs, enzymatic cleaners, alcohols and bleach; OR range: 2.50 – 12.08) and tasks (OR range: 2.58 – 3.97). Furthermore, a strong association was observed between higher asthma symptom scores and use of more sprays than wipes for fixed surface cleaning activities (mean ratio = 3.00; 95% CI: 1.50 – 5.98). Conclusion: This study has demonstrated that detectable exposures to OPA are higher and more isolated to certain departments than the more widespread low-level formaldehyde exposures present throughout the hospitals. Furthermore, cleaning agents have replaced NRL as important causes for WRA in health settings. Finally, specific cleaning agents such as OPA, quaternary ammonium compounds and enzymatic cleaners associated with medical instrument cleaning/disinfection as well as patient care activities and the use of sprays for fixed surface cleaning, are important environmental risk factors for various asthma-related outcomes among HWs in health care settings.
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    The study of occupational risk factors and interventions for baker's allergy and asthma among supermarket bakery workers
    (2013) Baatjies, Roslynn; Jeebhay, Mohamed Fareed; Heederik, Dick; Meijster, Tim
    Background: Baker's asthma is the most serious manifestation of occupational allergy among bakery workers. It is caused by IgE-mediated sensitisation and subsequent allergic reaction in the airways to specific occupational airborne allergens in flour or baking ingredients. Major aims of this study were to: characterise asthma phenotypes and environmental exposure to flour allergens among bakers and modifying factors; study associations between phenotype and environmental exposure and identify potential modifying factors of this association; determine the effectiveness of specific interventions in reducing exposure and the risk of sensitisation or allergic respiratory disease. Methods: A cross-sectional study was conducted among 517 bakery workers employed in 31 supermarkets. Health outcomes were assessed using a standardized questionnaire, immunological tests (sIgE, sIgG), methacholine challenge test and fractional exhaled nitric oxide (FeNO). Exposure assessment conducted pre- and post-intervention entailed determination of inhalable concentration of particulate mass and specific allergen levels. The intervention employed a group-randomised design to evaluate dust control measures. Results: Prevalence of probable occupational asthma (POA, 13%) was higher than atopic (AA, 6%), non-atopic (NAA, 6%) and work-aggravated asthma (WAA, 3%). Sensitisation to flour allergens was a major determinant of elevated FeNO among bakers. Bread bakers had the highest dust particulate (mean = 1.33 mg/m3) and allergen exposures. Exposure response relationships followed a bell-shaped curve, with the prevalence of IgE- sensitisation, allergic symptoms and POA, increasing up to 10-15 μg/m3 of airborne wheat allergen concentrations before declining. The association for IgE sensitization was not modified by IgG4 to wheat. The overall effect of the intervention revealed a 50% decrease in mean flour dust, wheat allergen and rye exposures in bakeries. Conclusion: Occupational asthma is the most common phenotype among supermarket bakery workers, with sensitisation to cereal flour allergens being the main determinant of allergic airway inflammation. The bell-shaped exposure response relationship is not modified by the presence of blocking antibodies and is probably due to a healthy worker effect. The multi-pronged intervention strategy was effective in reducing airborne flour dust and allergen levels. It is recommended that further studies investigate the long term health impact of these interventions in reducing the disease burden.
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    Work-related asthma among workers in the Mozambique wood processing industry
    (2021) Chamba, Paulino Samuel; Jeebhay, Mohamed Fareed; Baatjies, Roslynn
    Background: Workers in the wood processing industry are exposed to a heterogeneous mixture of inorganic and organic particles comprising wood fragments, viable and non-viable microorganisms, endotoxins, glucans and allergens, with the potential to cause work-related asthma. While this association has been reported in diverse settings, few studies have comprehensively studied host and environmental risk factors for work-related asthma phenotypes associated with wood dust. The aim of this study was to determine the prevalence and risk factors for work-related asthma among workers in the Mozambiquan wood processing industry. Methods: A cross-sectional study of wood workers was conducted in 21 factories located in three Mozambiquan provinces that processed various indigenous wood species. The environmental exposure assessment component comprised systematic walk-through inspections of all factories and the measurement of inhalable wood dust to determine particulate, (1-3)-β-D-glucan and endotoxin concentrations. A random sample of 30 workers were selected from similarly exposed groups (EGs) working in 9 representative factories for personal environmental sampling using PAS-6 sampling heads connected to Gillian GilAir pumps. A total of 124 of personal inhalable dust samples were collected for analysis. For the health outcome assessment, 450 subjects completed an ECRHS questionnaire adapted for occupational studies and underwent spirometry accompanied with bronchial reversibility and fractional exhaled nitric oxide (FeNO) testing conducted during the work shift. In addition, sera were obtained to determine the atopic status of workers using the Phadiatop test. Multivariate multiple lean and logistic regression was conducted adjusting for known confounders in saturated models using STATA 12 computer software. Results: The environmental exposure assessment demonstrated that the mean inhalable concentrations were 3.29 mg/m3 (GSD: 3.04) dust particulate, 98 endotoxin units (EU)/m3 (GSD: 5.05) and 123 ng/m3 (1-3)-β-D-Glucans (GSD: 5.05). These concentrations are higher compared to international exposure standards, generally ranging between 0.5-5 mg/m3 for dust particulate and 90 EU/m3 for endotoxins. A significant (p<0.05) modest correlation was observed between dust particulate and endotoxin (Pearson r = 0.48) and glucan (r = 0.40) concentrations. In the multivariate models, certain wood species were significantly associated with increased inhalable dust particulate levels - mahogany bean (Afzelia quanzensis Welw) (GM ratio=3.39) and African sandalwood (Spirostachys Africana Sonder) (GM ratio=3.19), as was factory building features (closed and semi-closed buildings, GM ratio=2.14). Additional determinants of elevated endotoxin exposures included African sandalwood (GM ratio=9.21) and working in closed buildings (GM ratio=2.10), while working in semi-closed buildings (GM ratio=2.14) was the main determinant of elevated glucan levels. Damp cloth cleaning methods were associated with lower dust particulate (GM ratio=0.55), endotoxin (GM ratio=0.32) and glucan (GM ratio=0.53) levels. The health outcome assessment of study subjects found the mean age to be 38 years, mostly male (94%), a large proportion non-smokers (76%) and 50% were atopic. The prevalence of current asthma was 7%, with equal proportions of atopic and non-atopic asthma (4%), while 2% had work-related asthma. The main host factors associated with work-related asthma outcomes were age, gender and atopic status. Exposure to Missanda (Erythrophleum suaveolens Brenan), Panga-panga (Millettia Stuhlmannii Taub.) and Mahogany bean (Afzelia quanzensis Welw.) wood species was associated with work-related ocular-nasal symptoms, while Mutondo (Cordyla Africana) species was associated with both work-related ocular-nasal and asthma symptoms. Work-related ocular-nasal symptoms were also associated, in a dose-dependent manner, with EGs categorized according to job titles as well as current dust particulate levels (medium, 4.68-4.71 mg/m3: OR = 3.45, 95% CI: 1.21 – 10.63; high, >4.71 mg/m3: OR = 3.66, 95% CI: 1.19 – 11.26) when compared to the low EG (<4.68 mg/m3) in unadjusted models. A similar trend was observed in the multivariate models adjusted for age, gender and smoking status. A history of work-related asthma symptoms was also positively associated with mean cumulative dust particulate exposure calculated across all jobs in the factory (OR = 1.01, 95% CI: 1.00 – 1.02) in multivariate linear regression models. In both unadjusted and adjusted models, increasing degree of bronchial reversibility was associated with increasing current dust particulate levels (medium, 4.68-4.71 mg/m3: OR = 1.99, 95% CI: 1.25 – 3.22; high, >4.71 mg/m3: OR = 1.73, 95% CI: 1.07 – 2.80) when compared to the low EG (<4.68 mg/m3). Increasing FeNO was associated with cumulative dust exposure quartiles based on current job >10.09 mg/m3-yr in both unadjusted (Q2, OR = 1.23, 95% CI: 1.02 – 1.51; Q3, OR: = 1.11, 95% CI: 0.91 – 1.35, Q4, OR= 1.23, 95% CI: 1.02 – 1.49) and adjusted models. Conclusion: This study demonstrated that exposure to all wood dust components in Mozambiquan wood processing workers were above international standards. The 7% asthma prevalence is consistent with global and specifically African country estimates, while 2% had work-related asthma. Processing of particular indigenous wood species and exposure metrics based on current as well as cumulative inhalable wood dust exposures were associated with an increased risk of work-related ocular-nasal and asthma symptoms, bronchial reversibility and airway inflammation. These risks are modified by host-associated factors of age, gender and atopy.