2
Toxic Chemicals
chemicals and their release. One reason is that elimination or reduction of use of a
chemical below the level of required reporting eliminates a company from having to
go through the process of calculating release and reporting. This saves on the cost
of compliance as well as adverse publicity and public response to a reported release.
The effects of the TRI program itself on reducing release are presented in Chapter 5.
Although the TRI program has resulted in some degree of reduction of the use of
individual chemicals and their release, the emphasis of the program has been on total
pounds chemical of released, not on the toxicity of those releases. Reports generally
stress total pounds of release or rank the chemicals released by total pounds. This,
in essence, assumes that chemicals are either toxic (and included in the inventory)
or not. In reality, not all chemicals included on the TRI list are equally toxic. It is
intuitively obvious that a pound of arsenic has more potential impact than a pound
of saccharin or nitrate, yet all three are included in the TRI and generally counted
equally. Companies find themselves in the news as having the most pounds of toxic
release to the community, with little analysis done on the actual risks associated with
the release.
To determine the toxic effect of a given release, a toxicologist looks at the pathway by which an individual or group is exposed to a toxin (i.e., oral ingestion for a
solid or liquid and inhalation for a gas or aerosol). Based on this pathway, a model of
dose is compared to cancer or noncancer toxicity dose-response factors, the weight
of the receptor, age, and other susceptibility factors to estimate risk to the individual
or group of individuals. There is a need for a simplified index for quantifying the
toxic impact of a chemical, one that can be used to evaluate the combined effects of
release of a TRI chemical, even if it is not used to determine the effect of an individual release. We need such an index so that individuals can determine their relative
and potential risk when evaluating chemical composition of products. We also need
this index to better evaluate the relative risks associated with TRI chemical release
and subsequently to prioritize chemicals for reduction based on their cumulative or
countrywide impact on the health of a nation. Chapter 6 utilizes available oral and
inhalation cancer and noncancer measures of toxicity to develop a method for the
relative ranking of toxicity (toxicity factor) for the TRI chemicals.
The impact of a chemical release is dependent not only on the toxicity of the
compound but also on the likelihood that it will be ingested or inhaled. The likelihood of a particular chemical being ingested or inhaled increases proportionally to
the mobility of the chemical, that is, its tendency to dissolve and enter the water we
drink or evaporate and enter the air that we breathe. The tendency to enter the water
is measured by its solubility. The tendency to evaporate is measured by its vapor
pressure. Chapter 7 presents the use of solubility and vapor pressure data to develop
a mobility factor, to be integrated into the toxicity factor for each TRI chemical.
A chemical that is persistent, that is, does not degrade or decompose in the
environment, will accumulate in the environment over time, increasing the potential
for exposure compared with a chemical that rapidly degrades. A measure of how
rapidly a chemical decomposes is the half-life or time needed for half of a given
amount of the chemical to degrade. Chapter 8 presents data on the half-lives of the
TRI chemicals as well as a method for converting these to a persistence factor, which
is then integrated into the toxicity factor for each TRI chemical.
Toxic Chemicals
chemicals and their release. One reason is that elimination or reduction of use of a
chemical below the level of required reporting eliminates a company from having to
go through the process of calculating release and reporting. This saves on the cost
of compliance as well as adverse publicity and public response to a reported release.
The effects of the TRI program itself on reducing release are presented in Chapter 5.
Although the TRI program has resulted in some degree of reduction of the use of
individual chemicals and their release, the emphasis of the program has been on total
pounds chemical of released, not on the toxicity of those releases. Reports generally
stress total pounds of release or rank the chemicals released by total pounds. This,
in essence, assumes that chemicals are either toxic (and included in the inventory)
or not. In reality, not all chemicals included on the TRI list are equally toxic. It is
intuitively obvious that a pound of arsenic has more potential impact than a pound
of saccharin or nitrate, yet all three are included in the TRI and generally counted
equally. Companies find themselves in the news as having the most pounds of toxic
release to the community, with little analysis done on the actual risks associated with
the release.
To determine the toxic effect of a given release, a toxicologist looks at the pathway by which an individual or group is exposed to a toxin (i.e., oral ingestion for a
solid or liquid and inhalation for a gas or aerosol). Based on this pathway, a model of
dose is compared to cancer or noncancer toxicity dose-response factors, the weight
of the receptor, age, and other susceptibility factors to estimate risk to the individual
or group of individuals. There is a need for a simplified index for quantifying the
toxic impact of a chemical, one that can be used to evaluate the combined effects of
release of a TRI chemical, even if it is not used to determine the effect of an individual release. We need such an index so that individuals can determine their relative
and potential risk when evaluating chemical composition of products. We also need
this index to better evaluate the relative risks associated with TRI chemical release
and subsequently to prioritize chemicals for reduction based on their cumulative or
countrywide impact on the health of a nation. Chapter 6 utilizes available oral and
inhalation cancer and noncancer measures of toxicity to develop a method for the
relative ranking of toxicity (toxicity factor) for the TRI chemicals.
The impact of a chemical release is dependent not only on the toxicity of the
compound but also on the likelihood that it will be ingested or inhaled. The likelihood of a particular chemical being ingested or inhaled increases proportionally to
the mobility of the chemical, that is, its tendency to dissolve and enter the water we
drink or evaporate and enter the air that we breathe. The tendency to enter the water
is measured by its solubility. The tendency to evaporate is measured by its vapor
pressure. Chapter 7 presents the use of solubility and vapor pressure data to develop
a mobility factor, to be integrated into the toxicity factor for each TRI chemical.
A chemical that is persistent, that is, does not degrade or decompose in the
environment, will accumulate in the environment over time, increasing the potential
for exposure compared with a chemical that rapidly degrades. A measure of how
rapidly a chemical decomposes is the half-life or time needed for half of a given
amount of the chemical to degrade. Chapter 8 presents data on the half-lives of the
TRI chemicals as well as a method for converting these to a persistence factor, which
is then integrated into the toxicity factor for each TRI chemical.