Scientific principles for evaluating the potential for adverse effects from chlorinated organic chemicals in the environment.
The term chlorinated chemicals is used to describe diverse groups of chemicals of varying chemical structure, including those used in water disinfection, as well as numerous aliphatic, aromatic, and polycyclic chlorinated substances. This report elaborates a number of scientific principles that govern the evaluation of the potential for chlorinated organic chemicals to cause adverse effects on the environment and to human health. The purpose of the report is to demonstrate the importance of applying these scientific principles in the evaluation of potential adverse effects of chlorinated organic chemicals. The four major principles upon which such a scientific analysis must be based are: (1) the fate and biological activity of a compound are determined by the chemical properties of the compound; (2) compounds do not show adverse effects below certain threshold concentrations, and the magnitude of response is related to dose; (3) inherent metabolic processes allow organisms to accommodate low doses of chlorinated organic chemicals; (4) observations associated with the presence of a certain compound must be biologically plausible effects, based on the specificity of the compound's activity in experimental systems. With respect to the first of these principles, there is abundant scientific evidence that the physical and chemical properties of chlorinated organic chemicals govern their bioaccumulative potential, toxicological properties, and thus their potential behavior and effects in the environment. Chemicals that have low solubility in water are highly lipophilic and have low vapor pressure, tend to accumulate in biological systems, and degrade slowly in the environment. Chlorinated organic chemicals that possess these characteristics include those having a carbon ring structure and multiple chlorine substitution. Other chlorinated organic chemicals with lesser degrees of chlorine substitution, such as 2,4-dichlorophenoxyacetic acid (2,4-D), trichlorophenol, chloroform, and dichloroethane, do not share the physical and chemical properties of the high molecular weight, cyclic, polychlorinated compounds and, as such, do not have the same potential to bioaccumulate. These differences among chlorinated organic chemicals with respect to their physical and chemical properties and behavior in the environment preclude the generalization that all organic chemicals containing chlorine behave similarly in the environment and act as persistent, bioaccumulative chemicals. The reactivity of chlorinated organic chemicals and hence their potential to produce biological effects depends on their specific molecular features. The substitution of chlorine into an organic molecule may increase or may reduce its biological activity.(ABSTRACT TRUNCATED AT 400 WORDS)
Willes
R F
RF
CanTox Inc., Mississauga, Ontario, Canada.
Nestmann
E R
ER
Miller
P A
PA
Orr
J C
JC
Munro
I C
IC
D000818:Animals; D004785:Environmental Pollutants / Q000032:analysis / Q000633:toxicity*; D006801:Humans; D006843:Hydrocarbons, Chlorinated / Q000737:chemistry / Q000633:toxicity*
D004785:Environmental Pollutants; D006843:Hydrocarbons, Chlorinated