Page 181 - Materials Chemistry, Second Edition

L1644_C04.fm Page 153 Tuesday, October 21, 2003 3:13 PM

decisions could be made based on the results of a risk assessment. In fact, risk-based
decision-making will generally result in the design of better environmental manage-
ment programs because risk assessment can produce more efficient and consistent
risk reduction policies; at the same time, it can also be used as a screening tool for
setting priorities.
Risk management based on the risk assessment result is the rpocess of deciding
what has to be done. Given the estimates of risk established, political and social
judgment is required to decide which risk is acceptable; therefore an acceptable risk
must be defined. On the other hand, risk assessment has several specific applications
that could affect the types of decisions to be made in relation to environmental
management programs. Further general discussion of some of the more prominent
applications scenarios is offered below.

4.9.1 ENVIRONMENTAL IMPACT ASSESSMENTS

Environmental impact assessment (EIA), as described in Chapter 1, is the analysis
of the likely environmental consequences associated with a determined human
activity. The main goal of an EIA is to ensure that environmental aspects are
incorporated into planning for decision-making on and implementation of develop-
ment activities. Typically, an identification of factors contributing the most to overall
risks of exposures to the environmental hazards of concern may be included. It may
also incorporate an analysis of baseline risks, as well as a consistent process to
document potential public health and environmental threats from the relevant activity.
EIAs are designed to prevent or minimize the adverse impacts of a development
activity while maximizing its beneficial effects.
As an example, quantitative risk assessment is often undertaken as part of the
siting process for newly proposed facilities. In many cases it is carried out as a
regulatory requirement for EIAs or, sometimes, is used for operating facilities to
evaluate implications from design changes or changes in exposure parameters. In
fact, the risk assessment of stack emissions from MSWI facilities seems to be one
of the most important applications for this type of evaluation. This becomes neces-
sary because MSWIs typically release various potentially toxic compounds — some
of which escape pollution control equipment and enter the outside air. These chem-
icals may include metals (e.g., arsenic, cadmium, and mercury), organic compounds
such as polychlorinated dibenzo(p)-dioxins and furans (PCDD/Fs) (Zemba et al.,
1996).

4.9.2 AIR TOXICS
An air pathway exposure assessment (APEA) is a systematic approach to address
air pollutant emissions from a variety of sources. This approach includes the appli-
cation of modeling and monitoring methods to estimate pollutant emission rates and
their concentrations in air. The goal of an APEA is to evaluate the extent of actual
or potential receptor exposures to air pollutants. This includes emission quantifica-
tion, modeling of environmental transport and fate by means of a determination of
the effects of the atmospheric processes on pollutant fate and transport, identification

© 2004 CRC Press LLC