PUBLIC HEALTH IMPLICATIONS OF THE INCINERATION PROCESS

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PUBLIC HEALTH IMPLICATIONS OF THE INCINERATION
PROCESS REVIEW OF THE EVIDENCERoy M.
HarrisonThe University of Birmingham
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• Overview
• Emissions and discharges from incineration
• Source pathway receptor relationships
• Evaluating the health evidence
• Conclusions

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• Emissions and Discharges
• Incinerators emit to atmosphere
• Sulphur dioxide
• Oxides of nitrogen
• Particulate matter (PM2.5 and PM10)
• Trace metals
• Toxic organic micropollutants (esp. dioxins,
  PCBs and polycyclic
• aromatic hydrocarbons (PAH))
• Incinerators generate solid ash residues
• Bottom ash
• Air pollution control residues
• These contain trace metals and TOMPs
• Incinerators discharge cooling water
• May be contaminated with trace metals and TOMPs

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WHICH PROCESSES PRODUCE WHICH POLLUTANT?
PROCESS POLLUTANT POLLUTANT POLLUTANT POLLUTANT POLLUTANT POLLUTANT POLLUTANT
PROCESS NOx SO2 PM HCl Metals Radioactive Dioxins PAH VOC
Power stations - coal fired - oil fired - gas fired Incinerator Cement works Motor car X X X X X X X X X X X X X X X X X X X X X X (X) X X - X X X X X - X X X X X X X
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• Abatement and Handling of Emissions
• Emissions to atmosphere are much reduced due to
  use of abatement plant which traps much of the
  acidic gases, particles, trace metals and organic
  compounds. Dioxin emissions are also limited by
  adjustment of combustion conditions.
• Solid waste residues (APCR) are treated as
  special waste and disposed to landfill. Good
  containment is essential.
• Aquatic discharges are subject to treatment and
  should not offer a source pathway receptor
  risk.

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• Evaluating the Risk
• The existence of emissions and discharges does
  not lead automatically to human exposure. There
  must be a plausible exposure pathway (a source
  pathway receptor linkage).
• It is essential to distinguish between
• Hazard The potential of a substance or
  activity to
• cause harm
• Risk The likelihood of that harm occurring

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• Evaluation of the Health Evidence
• There are two main approaches
• To look for an excess of disease in those exposed
  to incinerator emissions (epidemiology)
• To measure or calculate the exposures of local
  populations and to use exposure response
  coefficients to estimate a public health impact.

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• Epidemiology Establishing Causality
• Epidemiology establishes statistical
  associations between exposure (or some other
  factor) and disease. This is not the same as
  establishing a causal link.
• For epidemiological studies using a conventional
  95 statistical confidence interval, one result
  in 20 will be positive purely by chance even if
  no association exists.

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• Potential Health Risks of Incineration
• These lie in three main areas
• Cancer (various sites)
• Respiratory disease
• Reproductive outcomes (e.g. twins malefemale
  ratio congenital abnormalities, etc.)

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• Epidemiological Studies of Waste Incinerators
• Enviros/University of Birmingham review for
  DEFRA
• cancer outcomes 10 studies
• respiratory disease 6 studies
• reproductive outcomes 7 studies
• Many of the studies fail to distinguish
  adequately between hazardous waste and municipal
  incinerators.
• Most of the studies relate to emissions long ago
  when controls were far less stringent.
• The studies do not present a consistent case for
  any adverse health outcomes being caused by
  incinerator emissions.

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Epidemiological Studies of Waste Incinerators
The Small Area Health Statistics Unit Study

• SAHSU studied cancer incidence amongst 14
  million people living near 72 municipal solid
  waste incinerators in Great Britain over the
  period 1974 1987.
• The Department of Health Committee on
  Carcinogenicity was reassured that any potential
  risk of cancer due to residency (for periods in
  excess of 10 years) near to municipal waste
  incinerators was exceedingly low and not
  measurable by the most modern epidemiological
  techniques.

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• Epidemiology relating to Incinerators
• Respiratory Disease the studies provide little
  evidence to conclude the incinerators cause an
  excess in respiratory disease. This finding is
  not surprising given that incremental
  concentrations of air pollutants due to modern
  incinerators are small compared to the local
  background levels of air pollution due to traffic
  and other sources.
• Reproductive Outcomes twinning, sex ratios and
  congenital malformations have all have studied,
  but the only positive results are from studies
  which are inconclusive, or derive from massive
  exposures unrepresentative of modern incinerators.

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Evaluating the Health Impact Use of
Quantitative Exposure Response Functions

• The Committee on the Medical Effects of Air
  Pollutants (COMEAP) has used exposure response
  coefficients to calculate the public health
  impact of the classical air pollutants in urban
  areas of Great Britain.
• The COMEAP coefficients can, with reservations,
  be applied to the incremental pollution due to a
  point source of emissions.
• World Health Organisation unit risk factors for
  chemical carcinogens can be applied in a similar
  way.
• The calculations show a low level of risk
  associated with both the classical air pollutants
  and chemical carcinogens emitted from an
  incinerator.
• e.g. Annually for an incinerator sited in an
  urban area
• - deaths brought forward 0.008
• - respiratory hospital admissions 0.192
• - cancers (per 70 years) lt0.00005 for each
  carcinogen

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• Evaluating the Health Risk Dioxins
• The prevalent expert view in the UK is that
  dioxins exert a carcinogenic effect through a
  non-genotoxic mechanism.
• The implication is that there is a safe exposure
  level (a threshold) below which there is no
  cancer risk (unlike genotoxic carcinogens)
• The Tolerable Daily Intake recommended by the DH
  Committee on Toxicity is based on the most
  sensitive health endpoint reproductive and
  developmental effects. In their view, it will
  also protect against risk of other adverse
  effects, including carcinogenicity.

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• Do Incinerators increase the Human Body Burden of
  Dioxins?
• Work by Fierens and co-workers (2003) indicates
  that
• Dioxin in blood concentrations were determined
  in
• people residing close to an old incinerator in
  an industrialised
• area (I-I)
• people residing close to an old incinerator in a
  rural area (I-R)
• people from an unpolluted area (No-I)
• I-R group showed an elevation in dioxin levels
  relative to the other groups which had almost the
  same levels (I-I and No-I)
• Extrapolation from the data indicated that a
  significant increase in dioxin body burden is
  likely to occur only when dioxin emissions exceed
  5ng TEQ/Nm (c.f. the current regulatory limit of
  0.1 ng TEQ/Nm ).

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• Conclusions
• Epidemiology to date has not revealed
  significant public health problems with
  incinerators, despite focussing on an older
  generation of incinerators generating higher
  pollutant emissions.
• Indirect (COMEAP-type) estimation of adverse
  health outcomes shows there to be only a very
  small health impact.
• Current levels of incinerator emissions of
  dioxins are very unlikely to affect body burdens
  significantly, and no additional cancers are
  anticipated due to this pollutant.