Pollutants in a given medium are present in both quantity and quality and the space and time they are present all determine the risk factor they may represent. Assessment of pollutants is a highly technical issue and our attempt in this unit is to provide necessary information on the subject matter and a guide to the conduct of assessment.
Assessment of Pollutants
A pollutant is a waste material that pollutes air, water or soil. Three factors determine the severity of a pollutant: its chemical nature, the concentration and the persistence.
When we discuss the assessment of pollutants, we are either considering assessment to personal exposure or the level of impact on environmental media. For example high levels of air pollution are associated with adverse effects on public health.
Pollutants concentrations are typically subject to a high spatial and temporal variability. To investigate and quantify potential relations between pollutant concentrations and health effects, e.g. cases of respiratory diseases, sophisticated geospatial tools and methods are required.
Air pollutants are ubiquitous and a certain level of exposure is inevitable. For risk assessments and public health advice, however, it is necessary to quantify human exposure to specific pollutants of concern.
This is a challenging task as individual daily mobility patterns substantially influence exposure to air pollutants over time and in space. But it is not only peoples activities making the quantification difficult, also air chemistry, microclimatic and meteorological influences are changing over space and time, resulting in high spatial and temporal variation of ambient pollutant concentrations.
To analyze personal exposure the actual ambient concentration levels of the pollutant of concern are needed with sufficient temporal and spatial resolution. Recent development in GPS technology allows monitoring a person‘s individual activity patterns, and thus exposure to a specific pollutant, while moving in space and time.
The advantage of personal exposure profiles is that the actual concentration levels are measured. This is a highly localized approach which is suitable to assess short term effects of air pollution.
For further analysis this monitoring data needs to be integrated with temporal and spatially aggregated concentration data as well as with land use data to derive conclusions above associations between concentration levels, the environment the person is moving in and potential health impacts.
Risk Assessment is a step in a risk management procedure. Risk assessment is the determination of quantitative or qualitative value of risk related to a concrete situation and a recognised threat (also called hazard).
Quantitative risk assessment requires calculations of two components of risk(R), the magnitude of the potential loss (L), and the probability (p) that the loss will occur. In all types of engineering of complex systems sophisticated risk assessments are often made within Safety engineering and Reliability engineering when it concerns threats to life, environment or machine functioning.
Read Also: Sources and Types of Water Pollution
The nuclear, aerospace, oil, rail and military industries have a long history of dealing with risk assessment. Also, medical, hospital, and food industries control risks and perform risk assessments on a continual basis.
Methods for assessment of risk may differ between industries and whether it pertains to general financial decisions or environmental, ecological, or public health risk assessment.
Risk Assessment in Public Health
In the context of public health, risk assessment is the process of quantifying the probability of a harmful effect to individuals or populations from certain human activities.
In most countries the use of specific chemicals or the operations of specific facilities (e.g. power plants, manufacturing plants) is not allowed unless it can be shown that they do not increase the risk of death or illness above a specific threshold. For example, the American Food and Drug Administration (FDA) regulates food safety through risk assessment.
The FDA required in 1973 that cancer-causing compounds must not be present in meat at concentrations that would cause a cancer risk greater than 1 in a million lifetimes. The US Environmental Protection Agency provides basic information about environmental risk assessments for the public via its risk assessment portal.
In the estimation of risks, three or more steps are involved that require the inputs of different disciplines:
Hazard Identification is determining the qualitative nature of the potential adverse consequences of the contaminant (chemical, radiation, noise, etc.) and the strength of the evidence it can have that effect. This is done, for chemical hazards, by drawing from the results of the sciences of toxicology and epidemiology. For other kinds of hazard, engineering or other disciplines are involved.
Dose-Response Analysis is determining the relationship between dose and the probability or the incidence of effect (dose-response assessment). The complexity of this step in many contexts derives mainly from the need to extrapolate results from experimental animals (e.g. mouse, rat) to humans, and/or from high to lower doses.
In addition, the differences between individuals due to genetics or other factors mean that the hazard may be higher for particular groups, called susceptible populations.
An alternative to dose-response estimation is to determine an effect unlikely to yield observable effects, that is, a no effect concentration. In developing such a dose, to account for the largely unknown effects of animal to human extrapolations, increased variability in humans, or missing data, a prudent approach is often adopted by including safety factors in the estimate of the “safe” dose, typically a factor of 10 for each unknown step.
Exposure Quantifications determining the amount of a contaminant (dose) that individuals and populations will receive. This is done by examining the results of the discipline of exposure assessment. As different location, lifestyles and other factors likely influence the amount of contaminant that is received, a range or distribution of possible values is generated in this step. Particular care is taken to determine the exposure of the susceptible population(s).
Finally, the results of the three steps above are then combined to produce an estimate of risk. Because of the different susceptibilities and exposures, this risk will vary within a population.
In conclusion, assessment of pollutants is a very important activity in pollution control and our efforts to reduce the risk of exposure to dangerous pollutants. Pollution assessment involves highly technical skills and inputs by other professionals to determine the values of pollutants in any given situation.
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