6
Quantifying Toxicity
INTRODUCTION
Generally, the emphasis of the Toxics Release Inventory (TRI) program to date has
been on total pounds of releases, not on the toxicity of those releases. Reporting
on releases has generally stressed total pounds released and not been concentrated
on the toxicity of the individual chemicals. This in essence assumes that chemicals are either toxic and included in the inventory or they are not. All pounds are
equal. Toxicity varies widely for chemicals that are reported. It is intuitively obvious
that a pound of arsenic has more potential impact than a pound of saccharin, yet
both are included in the TRI, and generally both are reported equally. The U.S.
Environmental Protection Agency (USEPA) and state agencies have recognized a
need to concentrate on chemicals that have greater impact, with an increased emphasis on chemicals that are persistent, bioaccumulative, and toxic (PBT). The purpose
of this chapter is to develop a single toxicity factor (TF) for the chemicals in the
TRI inventory, which would be useful in ranking chemicals by their potential toxic
impact. The purpose of the TF would be to evaluate the relative toxic impacts of the
annual total release of a chemical.
This is an initial proposed approach; we welcome suggestions on how to improve
our analysis or use the same or additional toxicity data to relatively rank chemicals
differently. The important point to keep in mind is that the objective of this approach
was not to come up with an absolute number that we claim to represent the actual and
fixed toxic impact of a chemical. Rather, the proposed methodology was developed
solely for the purposes of coming up with a logical means of applying published and
routinely used toxicological data to then develop chemical-specific “toxicity” factors
to conduct an apples-to-apples comparison across chemicals. This would relatively
rank the potential effect among various toxic chemicals, such that reduction in the
use of toxic chemicals can be targeted and managed accordingly.
Toxicity values represent either acute or chronic impacts. Acute toxicity is the
measure of how a single or short-term dose of a compound can cause death or other
major impact. Chronic toxicity is the result of long-term ingestion or inhalation of a
much smaller dose of the chemical.
Acute exposure is handled well by current laws, such as those of the Occupational
Safety and Health Administration (OSHA). It is rare that the current public is
exposed to acute levels of toxins. Chronic levels are much lower and therefore likely
to be encountered by environmental releases or by the use of products containing
toxic chemicals.
There are four measures of chronic toxicity used in our analysis, based on method
of exposure and associated effect:
59
Quantifying Toxicity
INTRODUCTION
Generally, the emphasis of the Toxics Release Inventory (TRI) program to date has
been on total pounds of releases, not on the toxicity of those releases. Reporting
on releases has generally stressed total pounds released and not been concentrated
on the toxicity of the individual chemicals. This in essence assumes that chemicals are either toxic and included in the inventory or they are not. All pounds are
equal. Toxicity varies widely for chemicals that are reported. It is intuitively obvious
that a pound of arsenic has more potential impact than a pound of saccharin, yet
both are included in the TRI, and generally both are reported equally. The U.S.
Environmental Protection Agency (USEPA) and state agencies have recognized a
need to concentrate on chemicals that have greater impact, with an increased emphasis on chemicals that are persistent, bioaccumulative, and toxic (PBT). The purpose
of this chapter is to develop a single toxicity factor (TF) for the chemicals in the
TRI inventory, which would be useful in ranking chemicals by their potential toxic
impact. The purpose of the TF would be to evaluate the relative toxic impacts of the
annual total release of a chemical.
This is an initial proposed approach; we welcome suggestions on how to improve
our analysis or use the same or additional toxicity data to relatively rank chemicals
differently. The important point to keep in mind is that the objective of this approach
was not to come up with an absolute number that we claim to represent the actual and
fixed toxic impact of a chemical. Rather, the proposed methodology was developed
solely for the purposes of coming up with a logical means of applying published and
routinely used toxicological data to then develop chemical-specific “toxicity” factors
to conduct an apples-to-apples comparison across chemicals. This would relatively
rank the potential effect among various toxic chemicals, such that reduction in the
use of toxic chemicals can be targeted and managed accordingly.
Toxicity values represent either acute or chronic impacts. Acute toxicity is the
measure of how a single or short-term dose of a compound can cause death or other
major impact. Chronic toxicity is the result of long-term ingestion or inhalation of a
much smaller dose of the chemical.
Acute exposure is handled well by current laws, such as those of the Occupational
Safety and Health Administration (OSHA). It is rare that the current public is
exposed to acute levels of toxins. Chronic levels are much lower and therefore likely
to be encountered by environmental releases or by the use of products containing
toxic chemicals.
There are four measures of chronic toxicity used in our analysis, based on method
of exposure and associated effect:
59