Environmental risks and impacts - Environmental Deterioration and Contamination: Problems and their Management - page 197

Environmental risk assessment and impact assessment are closely related but dif-
fer in several points. Environmental risk is the combination of probability and size of
a possible damage originating from a certain risk source, e.g. a hazardous chemical
substance, a contaminated site, an accident or a catastrophe. It is a bilateral scenario
of the hazardous effect and the target environment. Environmental impact assessment
aggregates more (all) impacts on the targeted environment, including environmental,
economic and social impacts within the predetermined scope. Risk assessment applies
mainly quantitative tools, while impact assessment uses both quantitative and qualita-
tive methods. Risk assessment gives a stand-alone quantitative result whereas impact
assessment uses at least two scenarios: one shows the present situation without the
planned program or management measure; the other represents the scenario after the
program is introduced or the measure is taken. A quantitative risk score represents
input data of an impact assessment.
Assessment and analysis are also two terms which need some clarification. Assess-
ment means evaluation, judgment, or estimation using mathematical or modeling tools.
The result of assessment is a measure or score which is proportional to the value of the
assessed risk or benefit or any impact. Analysis means “the separation of an intellec-
tual or material whole into its constituent parts for individual study'' and “the study
of such constituent parts and their interrelationships in making up a whole''. One can
assess environmental risks or impacts, social and economic benefits, and can analyze
the inner structure, the distribution and nature of the compartments.
Environmental risk management is based on the conceptual risk model of an activ-
ity, an emission, a contaminated site or any environmental impact. The conceptual
model identifies the origin of the impact, the source of the risk (e.g. a new activity or a
hazardous agent), the possibly impacted area, and the target population. In case of a
hazardous emissions incident the conceptual model shows the pathways from diffuse
or point sources to the environmental compartments and from there further to natural
and agro-ecosystems as well as to humans. The principal pathways of emitted haz-
ardous materials are air, surface waters, groundwater as a key drinking water source,
soil affecting humans through the food chain, and surface waters as habitats for the
aquatic ecosystem. This kind of mapping of the “environmental scenario'' helps man-
agers to get a clear picture on the causes and possible environmental consequences
of natural disasters or man-made problems such as a new activity and “normal'' or
accidental emissions of dangerous agents or chemical substances from production, use,
waste disposal or contaminated land (see conceptual risk model in Figure 8.2). Scope
and scenario are arbitrarily chosen according to the nature of the problem. They can be
local, regional, watershed scale or global, and may focus on the ecosystem or humans,
on natural or residential land and on water or on soil. One can concentrate on the
effect of one hazardous agent/technology on a specific receptor (e.g. a pesticide on a
specific protected species), or on several impacts on complex environmental, social
or economic systems. Life cycles of substances, products and services must always
be taken into consideration because the different life stages may have rather different
impacts: hazardous chemicals in a well-controlled industrial facility, for instance, may
represent low risk, while the risk they pose in households or at an abandoned disposal
site may be substantial.
Assessment and control of environmental risks and impacts should form a dynamic
system based on a tiered and iterative assessment, continuous monitoring and an