Module 4: Organic Dusts - Health Effects Of Grain Dust
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HEALTH EFFECTS OF GRAIN DUST:

Effects of grain dusts on the lung:

The effects of grain dust on the lungs are difficult to define precisely because:

  1. The complex nature of the dust.
  2. The spectrum of clinical syndromes it causes.
  3. The difference in the characteristics of exposure to grain dust in various occupations.
  4. The multitude of pathogenetic mechanisms.
  5. The changing pattern of illness with progressive reduction in exposure.
Levels of ambient particles:

The levels of ambient particles in grain elevators depend on:

  1. The type of grain handled.
  2. The degree of activity.
  3. The efficiency of engineering controls (exhaust ventilation) and housekeeping practices.
Composition of grain dust:
  1. Various grains (wheat, oats, barley, rye etc.)
  2. Microflora (Cladosporium, Alternaria, Ustilago, Aspergillus, Mucor, Gram negative bacteria).
  3. Mites (Glycyphagus, Tyrophagus, Acarus, Goheiria).
    Note: House dust mites are NOT found in grain dust.
  4. Inorganic matter (soil, silicon dioxide, trace elements).
  5. Herbicides and pesticides (Aluminium phosphide).
  6. Animal matter (weevils, insects, rodents and birds excreta).
Physical properties:

Particle size of wheat/barley dusts: 10 µm (diam); wheat starch grains 10-40 µm (diam).

Biochemical properties:
  1. Histamine release.
  2. Activation of complement (d.t grain-derived tannin).
  3. Neutrophil chemotaxis.
  4. Lymphocyte stimulation (prod. interlukin-1).
Clinical syndromes:
  1. Acute effects:
  2. Chronic effects:

ASTHMA:

Allergens identified:
Antigen identification for a specific grain e.g. wheat:

ASTHMA-LIKE SYNDROME:

GRAIN FEVER:

CHRONIC OBSTRUCTIVE LUNG DISEASE:

OTHER HEALTH CONDITIONS ASSOCIATED WITH GRAIN DUST:

Silo fillers lung:

Organic dust toxic syndrome:

PREDISPOSING HOST FACTORS:

Importance of environmental factors and host factors depend on the type of clinical syndrome. For grain fever and asthma-like syndrome (across-shift changes in lung function), the degree of exposure is more important. For grain dust asthma, host susceptibility factors are more important. These include:

  1. Atopy (response to more than one common aeroallergen).
  2. Smoking (additive/synergistic effect).
  3. Alpha-1-Antitrypsin deficiency.
  4. Non specific bronchial hyperreactivity.

ENVIRONMENTAL FACTORS:

REFERENCES:

  1. Chan-Yeung M, Enarson D, Kennedy S. Sate of the Art - The impact of grain dust on respiratory health. Am Rev Resp Dis 1992; 145:476-487.
  2. O'Hollaren MT. Bakers' asthma and reactions secondary to soybean and grain dust. In: Bardanna EJ, Montanaro A, O'Hollaren AT, eds. Occupational asthma. Hanley & Belfus, Inc, 1992;107-116.
  3. Chan-Yeung, Kennedy S, Schwartz D. Grain dust induced lung disease. Asthma in the Workplace. Eds Bernstein IL, Chan-Yeung M, Malo JL and Bernstein DI. Marcel Decker Inc. (2nd ed) 1999; 32:617-633.
  4. Jeebhay MF, Stark J, Fourie A, Robins T, Ehrlich R. Grain dust allergy and asthma among grain mill workers in Cape Town. Current Allergy and Clinical Immunology, 13(3), 23-25, 2000.

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Postgraduate Diploma in Occupational Health (DOH) - Modules 3 – 5: Occupational Medicine & Toxicology by Prof Rodney Ehrlich & Prof Mohamed Jeebhay is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License.
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