Intake fraction is a measurement of pollution and it can be used in the determination of the
environmental health
Environmental health is the branch of public health concerned with all aspects of the natural and built environment affecting human health. In order to effectively control factors that may affect health, the requirements that must be met in ...
impact of a pollutant source. Intake fraction is the ratio of the mass of a pollutant inhaled or ingested to the mass of the pollutant emitted. Traditionally, scientists and policy makers have used a source-oriented approach to reduce health impacts from pollution. That is, they identified the largest producers of various pollutants and worked to reduce the amount of pollutants emitted.
Exposure assessment
Exposure assessment is a branch of environmental science and occupational hygiene that focuses on the processes that take place at the interface between the environment containing the contaminant of interest and the organism being considered. ...
, also referred to as exposure analysis, is a receptor-oriented science, and practitioners in this field focus on the sources of pollutants that result in the largest human exposure. The same principles can be used to assess pollutant impact on non-human organisms, but most exposure analysts focus on humans.
Definition
Intake fraction is the total mass of a pollutant ingested or inhaled by all exposed individuals over a given time, per total mass of the pollutant emitted. The intake fraction can be divided into components that identify the specific pollutant source, route, media, and subpopulation of exposed individuals. For example, policy makers may be interested in the total mass of mercury emitted by one specific coal-burning electric generator that is ingested in water by the residents living below the
poverty level
The poverty threshold, poverty limit, poverty line or breadline is the minimum level of income deemed adequate in a particular country. The poverty line is usually calculated by estimating the total cost of one year's worth of necessities for t ...
in one specific town.
Mathematically, intake fraction can be represented by the mass of pollutant intake divided by the mass of pollutant emitted:
Intake Fraction = Mass of Pollutant Intake (summed over all exposed individuals) / Mass of Pollutant Emitted
Determination
Direct measurement of intake fraction would only be reasonably possible in very specific, small scale situations. For example, direct measurement of
carbon monoxide
Carbon monoxide (chemical formula CO) is a colorless, poisonous, odorless, tasteless, flammable gas that is slightly less dense than air. Carbon monoxide consists of one carbon atom and one oxygen atom connected by a triple bond. It is the simple ...
from a space heater in a small house with three occupants could be achieved if each of the occupants used a personal CO monitor. Most situations of interest are too complicated to measure directly and modeling is used to estimate intake fraction. The models take into account the mass of pollutant released from the source, the horizontal and vertical distance between the point of emission and the exposed individuals, atmospheric conditions for outdoor sources, number of exposed individuals, and the time of exposure for these individuals.
Applications
The health impact of a pollutant source can be represented by the product of the total mass of a pollutant emitted, the intake fraction of the pollutant, and the toxicity of the pollutant. In the form of an equation:
Health Impact = Total Mass Emitted * Intake Fraction * Toxicity
Policy makers can use the intake fraction from various sources of a pollutant to determine which source will yield the largest return on the investment to reduce the pollutant. For example, an
oil drilling
An oil well is a drillhole boring in Earth that is designed to bring petroleum oil hydrocarbons to the surface. Usually some natural gas is released as associated petroleum gas along with the oil. A well that is designed to produce only gas may ...
facility may emit far greater mass of pollutants than a refueling station. However, if the oil drilling is located on a platform 10 miles offshore and the refueling station is in an urban area, then very few people will be exposed to the emitted pollutants. A relatively small reduction in emissions from the refueling station may yield a larger reduction in health impact than a large reduction at the oil platform.
Policy makers may also be interested in comparing the intake fraction among various groups within the population to assess
environmental justice
Environmental justice is a social movement to address the unfair exposure of poor and marginalized communities to harms from hazardous waste, resource extraction, and other land uses.Schlosberg, David. (2007) ''Defining Environmental Justic ...
. For example, it may be of interest to determine the intake fraction of
low-income
Poverty is the state of having few material possessions or little
residents of a town versus high-income residents of the town.
References
* Exposure Analysis by Wayne Ott, Anne Steinemann, and Lance Wallace,
Taylor & Francis
Taylor & Francis Group is an international company originating in England that publishes books and academic journals. Its parts include Taylor & Francis, Routledge, F1000 (publisher), F1000 Research or Dovepress. It is a division of Informa ...
.
* Intake fraction distributions for indoor VOC sources in five European cities. Ilacqua V, Hänninen O, Kuenzli N, Jantunen MF. Indoor Air. 2007 Oct;17(5):372-83.
US Department of Energy
The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United States. ...
, Environmental Energy Technologies Division, Indoor Environment Department.
* http://en.opasnet.org/w/Main_Page. National Institute for Health and Welfare, Finland
Environmental health