|
|
|
Commentary: Toxicologic Principles Do Not Support the Banning of Chlorine
“Toxicologic Principles Do Not Support the Banning of Chlorine: A Society of Toxicology Position Paper.” Fundamental and Applied Toxicology. Karol, M. H.3 (1995). 24.1–2
Commentary
1This document was prepared in consultation with the SOT ad hoc
Chlorine Working Group. Members of the group were J. P. Kehrer (SOT
Mechanisms Specialty Section), J. C. Lamb (SOT Regulatory Affairs
and Legislative Assistance Committee), J. A. Moore (SOT Risk Assessment
Specialty Section), J. Zurlo ( SOT Committee on Public Communications)
and J. I. Goodman, Chair (SOT Council Liaison to the Specialty Sections).
2Affiliations: J. P. K., Division of Pharmacology and Toxicology,
University of Texas at Austin, TX; J. C. L., Jellinek, Schwartz
& Connolly, Inc., Washington, DC; J. A. M., Institute for Evaluation
Health Risks, Washington, DC; J. Z., Department of Environmental
Sciences, Johns Hopkins University, Baltimore, MD; J. I. G., Department
of Pharmacology and Toxicology, Michigan State University, East
Lansing, MI; M. H. K., Department of Environmental and Occupational
Health, University of Pittsburgh, Pittsburgh, PA.
3President, Society of Toxicology.
Proposals have been made to develop a national strategy for substituting,
reducing, or prohibiting the use of chlorine and chlorine-containing
compounds based on the premise that such action would improve protection
of human health and the environment (International Joint Commission,
1994; US Environmental Protection Agency, 1994). The Council
of the Society of Toxicology (SOT), the governing body of the Society,
views these proposals as being contradictory to the principles on
which the science of toxicology is based.
The SOT is a professional organization composed of scientists (almost
5,000) from academia, government, non-governmental organizations
and industry who are engaged in various areas of toxicology. The
toxicologist is specially trained to examine the nature of the adverse
effects of chemical and physical agents on living organisms and
the chemical and physical agents on living organisms and the environment.
Toxicologists investigate the mechanism of action on the agent under
consideration and assess its potential to cause adverse effects.
The literal definition of toxicology the study of poisons is somewhat
simplistic in that it implies that we know which substances are
toxic and which are not. In fact, a truism that has endured for
about 500 years is that essentially every chemical, either alone
or in combination with other chemicals—in sufficient doses—is
capable of producing an adverse effect. In more familiar terms,
the dose makes the poison. Chemicals may have beneficial effects
at some doses and adverse effects at others. A responsibility of
the toxicologist is to define the potential toxic effects that chemicals
can induce and to determine the conditions of use that minimize
or prevent these effects so that the beneficial attributes of chemicals
can be realized safely.
Some chlorinated compounds may present a justifiable health concern
and indeed, some (e.g., DDT) have been banned. However, a comprehensive
strategy to eliminate a class of chemicals containing a common element
(e.g., chlorine) is simplistic and ignores the basic principles
of toxicology that govern risk assessment. In addition, it is important
to note that elimination of chlorine from the environment would
be impossible because there are many naturally occurring chlorine-containing
chemicals (including sodium chloride). The number of such that have
been identified that has expanded markedly in the past decade, e.g.,
30 naturally occurring chlorinated chemicals had been identified
in 1968 compared with 1500 in 1992 (Willes et al., 1993).
We should continue to conduct research to identify the potential
for chemicals to damage the environment and /or endanger human health,
ideally before they are released. The risk from a chemical exposure
can be predicted realistically only if there is adequate information
about the intrinsic toxicity of the chemical (including dose-response
data), the potential for exposure and the capacity for the chemical
to bioaccumulate and persist in the environment. Chlorinated chemicals
not only differ substantially in their toxic potencies, but they
also differ in their propensities to bioaccumulate and persist in
the environment. Thus, the mere presence of an element, e.g., chlorine,
does not automatically impart harmful properties to a chemical.
All chlorine-containing compounds are not equally hazardous. Therefore,
SOT takes the position that a broad-based ban of the class of chemicals
containing chlorine, or any other element for that matter, would
be both irresponsible and unscientific. Such a prohibition would
unnecessarily eliminate many beneficial chemicals from common use.
For example, the chlorination of drinking water in the vast majority
of US water systems has prevented untold numbers of illnesses
and deaths by killing pathogenic organisms found in the water supply.
The formation of low levels of potentially toxic chlorinate compounds
as a result of this process is certainly of concern and must be
minimized.
However, the estimate hazard posed by the trace amounts of these
materials that are produced is insignificant compared with that
from untreated water. Accordingly, the benefit of a chlorinated
water supply vastly outweighs its estimated risks. Other essential
uses for chlorinated compounds include hospital disinfection, plant
protection and the production of countless consumer products, including
pharmaceuticals and plastics. Therefore, before a ban of chlorinated
compounds (or a marked reduction of their use) can be considered
in realistic context, the feasibility of producing effective and
less toxic substitutes must be demonstrated. The concern surrounding
the use of chlorine and chlorine-containing compounds is related
at least in part to the large amount of information that has been
generated by research on the toxicities of some of the compounds
in this class. However, a similar body of evidence does not exist
(i.e., the studies have not been performed) for most alternative
compounds. Thus, before changes are made, the consequences of elimination
of a compound or the hazard of using another chemical to achieve
the same end must be considered.
The Society of Toxicology supports a comprehensive objective approach
to understanding the potential hazards of chlorine and chlorine-containing
compounds. It recognizes that there is a substantial body of evidence
that implicates some of these compounds as potential human and environmental
hazards. It is also aware that other, non-chlorinated, chemicals
have a similar or greater potential to cause harm. Consequently,
the SOT takes the position that the most responsible and scientifically
sound approach is to assess the toxicity of agents on a chemical
by chemical basis, rather than target one class of chemicals (e.g.,
chlorine-containing compounds) for study and elimination. The determination
of unacceptability should be based on scientific data that document
the adverse effects of exposure and a weighing of the risks vs.
benefits of using the chemical in question. Indeed, based upon sound
principles of toxicology, rational and effective assessments of
the potential toxicity of chemicals, including chlorinated chemicals,
are currently taking place and rigid standards exist for registration
of new products to which people will be exposed.
References
International
Joint Commission on the Great Lakes, Durnil, G. K., Lanthirt,
C., Cleveland, H. P., Goodwin, R. F., Macaulay, J. A. and Walker,
G. W. (Commissioners) (1994). Seventh Biennial Report on Great
Lakes Water Quality, Windsor, Ontario, Canada, February 1994.
US Environmental Protection Agency’s 1994 Recommendations in
the Pollution Discharge Prohibitions of the Clean Water Act Reauthorization,
as Transmitted to the Congress by the Executive Office, p.22,
February 1994, EPA 800-R-94-001. (A copy of this may be obtained
from the Society of Toxicology, 1821 Michael Faraday Drive, Suite 300, Reston, VA 20190.)
Willes, R. F., Nestmann, E. R., Miller, P. A., Orr, J. C. and
Munro, I. C. (1993). Scientific principles for evaluation the
potential for adverse effects from chlorinated organic chemicals
in the environment. Regul. Toxicol. Pharmacol. 18, 313–356.
|
