LISTS OF SUSPECTED TOXICANTS
Chemicals are identified as suspected toxicants based on reports in the
scientific or regulatory literature, or on information
abstracted from major toxicological databases. Lists of
suspected toxicants are available for twelve health effects.
Suspected toxicants possess evidence that they can cause specific
adverse health effects, but no authoritative hazard
identification is currently conducted by regulatory agencies or
scientific organizations for that health effect. Inclusion of a chemical on a "suspected" list should be viewed as a preliminary indication that the chemical may cause this effect, rather than a definitive finding that it does.
To identify suspected toxicants, information was abstracted from the
principal toxicology text books (such as Casarett and
Doull's Toxicology), medical journal review articles, regulatory
reports providing hazard information (such as rules justifying the
addition of chemicals to the U.S. Toxic Release Inventory), and international
chemical hazard resources (such as the European Economic Community's
List of Dangerous Substances). For further information about analyses of the National Institute for Occupational Safety and Health's Registry of the Toxic Effects of Chemical Substances (RTECS) database and the Carcinogenic Potency Database, see the description of Environmental Defense's Suspect Hazard Identification project.
The weight of toxicological or epidemiological evidence supporting
suspect hazard identification can vary significantly between chemicals.
For example, evidence from two different laboratory species indicates
that acetonitrile can cause cardiovascular toxicity. In contrast, there
is overwhelming evidence that carbon monoxide causes cardiovascular
toxicity in humans. On this website, these differing amounts of evidence
both lead to designation as a "suspected" toxicant, because no agency
authoritatively compiles lists of cardiovascular toxicants.
Identifications made by regulatory agencies or scientific references
have often undergone peer review, but no administrative process has
occurred that allows debate over the toxicity of a chemical to be
Health effect data sources rarely specify if a chemical is a health hazard by a specific route of exposure (for example, hazardous if inhaled, but safe if ingested). If there is evidence that a chemical can cause a health effect, this website generally assumes the chemical is a potential hazard by all routes of exposure.
These differences in amount of evidence and uncertainties about health effects will result in substantially greater debate about the validity of this website's suspected health effects lists than about its lists of recognized hazards. In many cases, there may be conflicting studies: some of which indicate an ability to harm health, and some which found no effect. Lists of suspected toxicants represent a screening-level evaluation of a chemical's capacity to adversely effect human health. The amount of evidence of reported adverse health effects is sufficient to comprise a strong "hazard signal" that warrants further action. The burden of proof should be on those who release these chemicals to the environment to produce toxicological evidence that demonstrates that these substances do not pose human health risks.
There are separate lists for recognized and suspected
carcinogens, developmental toxicants and reproductive toxicants. A number of chemicals have toxicological evidence of adverse health impacts that currently does not satisfy the criteria used to list agents under Proposition 65, or that has not yet been reviewed by the hazard
identification processes in the state of California. For example,
chemicals that have recently been identified as probable carcinogens by
the U.S. EPA or as reasonably anticipated to be carcinogens by the
National Toxicology Program are considered "suspected" carcinogens by
this website until they are officially incorporated into the Proposition 65
list of recognized carcinogens.