ORIGINAL ARTICLE

Agricultural seed dust as a potential cause of organic dust toxic syndrome

L A M Smit¹, I M Wouters¹, M M Hobo¹, W Eduard², G Doekes¹, D Heederik¹

¹ Institute for Risk Assessment Sciences (IRAS), Division of Environmental and Occupational Health, Utrecht University, the Netherlands
² National Institute of Occupational Health, Oslo, Norway

Correspondence to:
Correspondence to:
MsL Smit
Institute for Risk Assessment Sciences, Division of Environmental and Occupational Health, PO Box 80176, 3508 TD Utrecht, the Netherlands; L.Smit{at}iras.uu.nl

Aims: Episodes of serious work related health problems resembling organic dust toxic syndrome (ODTS) in workers of a grass seed quality inspection laboratory prompted the authors to study personal endotoxin exposure levels in this facility and in the agricultural seed processing industry. In addition, microbial and inflammatory characteristics of agricultural seeds were studied.

Methods: The authors assessed inhalable dust and endotoxin levels in 101 samples from 57 workers in grass, cereal, and vegetable seed plants who were handling mainly grass seeds as bulk product, and horticulture seeds in smaller quantities. Additionally, real-time dust exposure was measured using a DataRAM monitor in 12 grass seed workers to obtain more information on exposure patterns during specific tasks. Endotoxin concentrations in seed extracts were determined by LAL assay and seed samples were analysed by scanning electron microscopy. Release of inflammatory cytokines was measured in supernatants of whole blood samples stimulated with lipopolysaccharide (LPS) or agricultural seed extracts in a human whole blood assay (WBA).

Results: Endotoxin concentrations in personal samples were high (geometric mean 1800 EU/m³), particularly in the grass seed quality inspection lab where endotoxin levels up to 274 000 EU/m³ were measured. The recommended health based endotoxin exposure limit of 50 EU/m³ was amply exceeded in almost all personal samples. Job tasks dumping and mixing were associated with highest dust and endotoxin exposures, which was confirmed by real-time measurements. Microbial infestation was found in almost all seed samples. WBA results showed that most seed extracts were capable of inducing a pronounced dose dependent cytokine release.

Conclusions: Workers handling grass, cereal, or vegetable seeds are at risk of exposure to high levels of endotoxin containing seed dust. Occupational exposure to inhalable agricultural seed dust can induce inflammatory responses, and is a potential cause of ODTS.

Abbreviations: LAL, limulus amebocyte lysate; LOD, limit of detection; LPS, lipopolysaccharide; ODTS, organic dust toxic syndrome; SEM, scanning electron microscopy; WBA, whole blood assay

Keywords: endotoxin; occupational exposure; agricultural seed processing industry; ODTS; whole blood assay

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