5
Environmental Fate Models, with
Emphasis on Those Applicable to Air
5.1 Introduction
In the past, not much thought was given to the fate of a chemical when it was
released to the environment, as long as there was a perceived beneft (e.g.,
crop and residential pest control and the refnement of crude oil to provide
products for industry and public use). However, from about the mid-point
of the 20th century, there was a growing awareness that everything we
humans do will impact the Earth in some way, often to its and our detriment. For example, releases of DDT, PCBs, and dioxins to the environment
led to disastrous, nearly irreversible results. In addition, it was found that
these chemicals, and many others, undergo long-range transport to become
widely distributed in the environment. They persist and biomagnify in food
chains as well as leave residues in soil, water, and biota (seals, eagles, polar
bears—top-of-the-food-chain organisms, including humans). As a result of a
growing awareness that the Earth’s ecosystems are fragile, a grassroots environmental movement, sparked in part by Rachel Carson’s Silent Spring (1962)
(Carson, 1962), eventually led to the establishment of the U.S. Environmental
Protection Agency (EPA) in 1970.
A more proactive approach to lessening chemical impact on the environment would be to predict the behavior and fate of a chemical before its use.
With regard to this, the establishment in 1976 of the U.S. EPA Toxic Substances
Control Act (TSCA), which requires extensive testing of substances before
they are released, represented a move in the right direction. Testing might
involve the use of empirical models in laboratory/feld chambers that are
spiked with the chemical(s) of interest. Historically, laboratory/feld chambers, along with direct measurements in the open environment, generated the
data that eventually were written into computer code. We now have numeric
computer-based models as an alternative to the strictly empirical approach.
Modeling a chemical’s potential behavior would go far in providing the
data needed to make a judgment regarding the possible risk to humans and
the environment. The modeling approach—chambers and computers—also
DOI: 10.1201/9781003217602-5
73
Environmental Fate Models, with
Emphasis on Those Applicable to Air
5.1 Introduction
In the past, not much thought was given to the fate of a chemical when it was
released to the environment, as long as there was a perceived beneft (e.g.,
crop and residential pest control and the refnement of crude oil to provide
products for industry and public use). However, from about the mid-point
of the 20th century, there was a growing awareness that everything we
humans do will impact the Earth in some way, often to its and our detriment. For example, releases of DDT, PCBs, and dioxins to the environment
led to disastrous, nearly irreversible results. In addition, it was found that
these chemicals, and many others, undergo long-range transport to become
widely distributed in the environment. They persist and biomagnify in food
chains as well as leave residues in soil, water, and biota (seals, eagles, polar
bears—top-of-the-food-chain organisms, including humans). As a result of a
growing awareness that the Earth’s ecosystems are fragile, a grassroots environmental movement, sparked in part by Rachel Carson’s Silent Spring (1962)
(Carson, 1962), eventually led to the establishment of the U.S. Environmental
Protection Agency (EPA) in 1970.
A more proactive approach to lessening chemical impact on the environment would be to predict the behavior and fate of a chemical before its use.
With regard to this, the establishment in 1976 of the U.S. EPA Toxic Substances
Control Act (TSCA), which requires extensive testing of substances before
they are released, represented a move in the right direction. Testing might
involve the use of empirical models in laboratory/feld chambers that are
spiked with the chemical(s) of interest. Historically, laboratory/feld chambers, along with direct measurements in the open environment, generated the
data that eventually were written into computer code. We now have numeric
computer-based models as an alternative to the strictly empirical approach.
Modeling a chemical’s potential behavior would go far in providing the
data needed to make a judgment regarding the possible risk to humans and
the environment. The modeling approach—chambers and computers—also
DOI: 10.1201/9781003217602-5
73