Waste management and public health: the state of the evidence

Appendix 2.2 Incineration

 

1. Have studies been done on human populations?

 

Yes.

The literature search yielded 50 primary studies and three reviews (Allsopp et al, 2001, Hu and Shy, 2001, National Research Council, 2000). The majority were studies on communities but there were 14 occupational health studies.

All types of health outcomes were investigated, including: Cancer (15 studies), Health problems/diseases/unspecified health effects (12 studies), Biomarkers (10 studies), Reproductive outcomes/developmental effects on children (9 studies), Symptoms (8 studies), Mortality (5 studies), Injuries/poisoning (3 studies), Psychosocial impacts (2 studies), Economic (1 study).

 

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.

Among the occupational health studies, there were 3 studies where exposure was presumed from occupation in the incinerator;  two studies with quantified ambient measurements of PM10 (particulates) or metals; and 7 studies providing quantified personal measurements (of blood levels of lead or of urinary mutagens). There was not enough information about the remaining two studies to categorise the exposure data.

Among the studies of communities living near to incinerators, 4 used quantified ambient measurements, 2 used quantified estimates and 27 studies used residence as a proxy measure of exposure.

 

3. Are there ANY hypothesis-testing studies?

 

Yes.

The following were hypothesis-testing studies:

1.       An occupational health study of a cohort of incinerator workers with high, medium and low exposure to toxic compounds such as metals (Bresnitz et al, 1992),

2.       A study simultaneously measuring air quality and respiratory function and symptoms in populations living in the neighborhood of waste incinerators compared with three matched-comparison communities. (Shy et al, 1995)

3.       A study of six communities in southwestern North Carolina investigating the respiratory health status of residents whose households are located near an incinerator. This diary study estimated the daily variation of pulmonary function measured as peak expiratory flow rate (PEFR) related to 24-h mean PM10 levels, which were observed at each monitoring station placed in the six study communities, as a surrogate exposure measure of outdoor air pollution. This study did not show any difference in respiratory health between subjects of an incinerator community and those of its comparison community. (Lee and Shy, 1999)

4.       Study of 713 children in 2 regions near 2 sludge burning incinerators in Sydney. Controls were 626 children in a region with no incinerator. Exposure assessment by air monitoring and region of residence. Outcomes - prevalence of respiratory illness, airway hyperresponsiveness, atopy, FEV1. Results - no significant differences in baseline FEV1 and prevalence of current asthma, atopy, symptom frequency or severity of asthma illness between study and control regions. (Gray et al, 1994)

 

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

 

Yes.

For example, the study by Lee & Shy (1999)  analyzed how health outcomes varied according to the degree of exposure to ambient pollutants as well as to other cofactors including, sex, age, respiratory hypersensitivity, hours spent outdoors within the area of the selected community, and surrogate measures for indoor air pollution exposure (vacuum use and experience of air irritants at work).

 

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

 

No.

The 4  hypothesis-testing studies consistently showed no association between the hazards from incineration and any health outcomes. Even among the hypothesis-generating studies, the results were inconsistent. Roughly half the primary studies found an increase in the incidence of a health problem and half did not.

Using the algorithm above, we judged the evidence linking incineration with any health outcomes as insufficient.