Exposure to Microorganisms and Aeroallergens among Greenhouse Workers Worldwide and Associated Respiratory Diseases

Greenhouse operations are an important sector of the horticulture industry, also known as the Green Industry, accounting for nearly 2 million US jobs and about $148 billion in output. It is a work environment that can result in increased exposure to respiratory hazards because of its fundamentally enclosed nature. In addition, high concentrations of bioaerosols may be aerosolized by work activities in greenhouses. Thus, this is a large industry with potential for exposure to high concentrations of bioaerosols and associated respiratory diseases among workers. Our previously completed CDC-NIOSH project revealed that workers in some US greenhouses were exposed to elevated levels of airborne microbial contaminants. The prevalence of self-reported respiratory symptoms was generally higher among greenhouse workers than among controls. Studies from some European countries also reported significant associations between bioaerosol exposures and respiratory diseases among workers including occupational asthma. Bioaerosol exposure levels in greenhouses of different countries and associated allergic rhinitis and asthmatic disorders have been discussed in this review article. Large scale studies are warranted to gain a better understanding of the associations between exposures in greenhouses and the development of rhinitis and lower respiratory symptoms, particularly in the United States and many other countries. This review article will provide vital information on the current data and data gaps in exposure levels of airborne microorganisms and aeroallergens in greenhouses, associated rhinitis and other respiratory disorders, and future research directions.