Waste management and public health: the state of the evidence

A2.3 Composting

 

1. Have studies been done on human populations?

 

Yes.

Two review papers were found (Maritato et al, 1992, Environment Agency, 2001) and 11 primary studies.

 

2. Have hazards been identified? Does the appearance of the hazard precede the health outcome? Is the association biologically plausible? Is there data on exposure?

 

Yes.

The main hazards identified from composting are bioaerosols containing bacteria such as Clostridium botulinum and endotoxin-producing Gram negative bacteria and/or fungal spores such as Aspergillus fumigatus. The main health impacts from composting (Bunger et al, 2000) are:

•   Inflammatory responses of the upper airways – congested nose, sore throat and dry cough

•   Toxicoses – toxic pneumonitis due to endotoxins

•        Infections – respiratory tract and skin

•        Allergies - bronchial asthma, allergic rhinitis, extrinsic allergic alveolitis (hypersensitivity pneumonitis)

 

The association between bioaerosols and these health outcomes is biologically plausible. The route of exposure is inhalation. The data on exposure is measurements of specific IgG antibodies to fungi and bacteria as immunological markers of exposure to bioaerosols.

 

 

3. Are there ANY hypothesis-testing studies?

 

Yes.

There is a case control study (Bunger et al, 2000) which found that the compost workers had significantly more symptoms and diseases of the airways (p=0.003) and the skin (p=0.02) than the control subjects. They had significantly increased antibody concentrations against fungi and actinomycetes. No studies were found about the health impacts to residents living by composting facilities.

 

4. Have any of the hypothesis-testing studies controlled for possible confounding factors?

 

Yes

The participants were interviewed for work related symptoms, conditions of exposure to bioaerosols at their workplaces, exposure to bioaerosols from other sources, atopic diseases, and smoking habits.

 

 

5. Are there more than 20 hypothesis-testing studies consistently showing strong or moderate relative risks?

 

No.

Only one case-control study was found. The rest were case reports or hypothesis-generating studies.

Regarding occupational exposure, it is possible that composting causes health problems. But the evidence is insufficient regarding residence near composting facilities.