Mite, insect sensitization prevalent among greenhouse workers
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Greenhouse workers experienced high levels of sensitization to insects and mites used for biological pest control where they work, according to a cross-sectional study published in The Journal of Allergy and Clinical Immunology: In Practice.
“We have seen many greenhouse workers with suspicion of occupational disease (asthma, rhinitis, contact urticaria and hand eczema) in the occupational medicine clinic of the Finnish Institute of Occupational Health,” Hille Suojalehto, MD, PhD, chief respiratory physician at the Finnish Institute of Occupational Health in Helsinki, Finland, told Healio.
“Many of these patients have been sensitized to pest control organisms, and we have been able to diagnose occupational disease to these organisms in some of them. In this study, we wanted to assess prevalence of sensitization to biological pest control organisms and pests among greenhouse workers,” Suojalehto said.
The wide use of biological pest control instead of chemical pesticides has many major benefits, Suojalehto continued, including reduced environmental pollution, occupational safety and food quality.
However, Suojalehto said it is difficult to compare the risks for worker sensitization with these benefits, and it seems unlikely that greenhouses would start using chemical pesticides again.
“My view is that we should find means to control exposure to allergens and reduce workers’ sensitization,” she said.
The study involved 117 tomato and cucumber greenhouse workers (median age, 39 years; interquartile range, 31-50; 62% men) — 107 employees and 10 entrepreneurs — from eight companies using biological pest control in Finland.
An occupational physician conducted face-to-face interviews with the workers about demographics, ethnicity, work history, smoking habits, and breathing and skin symptoms. Most were migrants from Eastern Europe and Southeast Asia, and 40 (34%) were current smokers.
“The greenhouse workers in Finland are mainly immigrant workers and often not aware of the risks,” Suojalehto said. “One of our main goals of this project was to increase workers’ awareness of the risks and introduce safe work methods.”
The interviews revealed atopy in 30 (25%) of the workers. In addition, 24 workers (21%) reported asthma, 49 (42%) had rhinitis and 14 (12%) displayed urticaria symptoms.
Twenty-five (22%) of the workers also demonstrated eosinophilic airway inflammation, as measured by fractional exhaled nitric oxide of 25 ppb or greater.
Researchers then assessed the workers’ sensitization to nine organisms commonly found in these greenhouses by serum-specific IgE measurement.
According to the findings, 58 of the workers (50%) were sensitized to one or more of the organisms tested. These workers more commonly were Southeast Asian (P < .001) and reported more asthma (P = .019) and rhinitis symptoms (P = .012) than the others.
The sensitized workers also showed an increase in eosinophilic airway inflammation (P = .015).
The researchers detected sensitization to one or more tested mites in 34 workers (29%), most commonly to Amblyseius swirskii (n = 29; 25%) and Suidasia medanensis (n = 29; 25%), with considerable overlap in mite sensitization.
Also, 54 workers (46%) were sensitized to one or more of the tested insects, with 25 workers (21%) sensitized to Hymenoptera — an order that includes sawflies, wasps, bees and ants — and 54 workers (46%) sensitized to Hemiptera, which includes cicadas, aphids, planthoppers, leafhoppers, bed bugs and shield bugs, among others. The most common sensitization to insects was to Macrolophus pygmaeus, occurring in 54 (46%) workers.
“We were surprised by the high prevalence of sensitization to these organisms. Half of the workers were sensitized,” Suojalehto said. “We were also surprised about the high prevalence (46%) of sensitization to the Macrolophus pygmaeus insect. Previously, sensitization to it has not been detected.”
Using logic regression, the researchers found sensitization to these mites and insects to be a significant risk factor for asthma symptoms (OR = 3.9; 95% CI, 1.2-12.5). There also was a trend toward association between mite and insect sensitization and rhinitis, but there was no signification association between sensitization and self-reported urticaria (OR = 1.2; 95% CI, 0.3-4.2).
Southeast Asian origin appeared to be a risk factor for rhinitis (OR = 2.8; 95% CI, 1.2-6.3) and for sensitization to pests and control organisms (adjusted OR = 5.1; 95% CI, 2.1-12.1).
Because the researchers could not confirm that all of the pest control products had been used recently in the greenhouses they studied, nor could they test all of the used pest control products, researchers noted they may have underestimated total sensitization rates among the workers.
Researchers are continuing their work by assessing Macrolophus pygmaeus allergens, Suojalehto said.
“We are also reporting occupational diseases caused by these organisms that have been detected in the occupational medicine clinic of the Finnish Institute of Occupational Health,” she said.
To prevent allergic diseases, the researchers recommended regular health surveillance and education among these workers, work modifications and the use of protective equipment.
“We instruct occupational health care to assess risks at the workplace, to advise greenhouse workers on allergy risks and symptoms and use of protective equipment, and to perform regular health surveillance to exposed workers,” Suojalehto said. “The recommendations are necessary to reduce sensitization of workers and to prevent occupational diseases.”
For more information:
Hille Suojalehto, MD, PhD, can be reached at hille.suojalehto@ttl.fi.