Module 4: Organic Dusts - Lecture

DEFINITION OF ORGANIC DUSTS:

Organic dusts can be defined as dusts of plant (vegetable), animal and microbial origin.

There are various sources of hazardous exposure to organic dust in the occupational setting (Table 1).

Contrary to common belief these dusts are not biologically inert and contain various major agents that may result in adverse health effects to exposed workers (Table 2). Some of the common agents are:

• endotoxins (gram negative bacteria);
• (1®3)-b-D-glucans (moulds);
• proteins (animal hair/urine/feces; grain) & enzymes which act as allergens;
• tannins, plicatic acid (western red cedar wood).

High-risk exposure groups:

• agricultural workers;
• nearby community residents;
• processing workers;
• consumers.

The main routes of exposure are:

• airborne;
• other: ? dermal/ocular.

These biological agents exert their effects through various different pathogenic mechanisms:

• Irritant effects (e.g. chemical decomposition);
• Immunologic viz. IgE-mediated; Type III/Type IV (allergens);
• Carcinogenic (mutagens).

There are various diseases caused by organic dusts/aerosols, which can be broadly categorised as:

1. Inhalation fever (fever, myalgia, fatigue);

2. a)Toxic pneumonitis
   b) Organic dust toxic syndrome;

3. Hypersensitivity pneumonitis (extrinsic allergic alveolitis);

4. a) Rhinitis, Conjunctivitis
   b) Asthma
   c) Asthma-like syndrome (acute functional response);

5. a) Chronic bronchitis
   b) Chronic obstructive airways disease;

6. Nasopharyngeal cancer.

The most common adverse health outcomes are respiratory conditions among workers exposed to animals (Table 3) and plants (Table 4).