HEALTH EFFECTS|How this Website Identifies Health Hazards of Toxic Chemicals

To date, it has been difficult if not impossible to easily obtain information about the types of health hazards posed by toxic chemicals. While some regulatory agencies have generated lists of carcinogens and developmental and reproductive toxicants, these are often difficult to find and link to sources of information about chemical releases or exposure. If you are concerned about other important health effects - such as neurotoxicity or endocrine disruption - the lack of information is even more serious, as no authoritative scientific or regulatory agencies routinely categorize toxicological evidence in an attempt to identify these types of health hazards.

Scorecard makes hazard identification information far more accessible. An extensive review of the scientific literature and toxicological databases has been conducted to create lists of chemicals with evidence of a potential to adversely effect human health. These lists cover the following types of diseases or adverse impacts on specific physiological systems: cancer, cardiovascular or blood toxicity, developmental toxicity, endocrine toxicity, gastrointestinal or liver toxicity, immunotoxicity, kidney toxicity, musculoskeletal toxicity, neurotoxicity, reproductive toxicity, respiratory toxicity, and skin or sense organ toxicity. The Health Effects section provides links to a definition of each of these health effects, a list of chemicals recognized or suspected of causing each effect, and the references used to compile these lists.

The website contains two types of lists based on this extensive review and analysis:

Chemicals are identified as recognized toxicants based on the hazard identification efforts of authoritative national and international scientific and regulatory agencies. To date, such efforts have been focused on only three types of toxicity: cancer, reproductive toxicity, and developmental toxicity. The website utilizes lists developed under California's Proposition 65 (which combine the hazard identification efforts of various authoritative bodies) as its primary reference for recognized toxicants. The
current Proposition 65 list of chemicals that are "known to the State of California" to cause cancer or reproductive toxicity is available online.

Chemicals are listed on Proposition 65 after scientific peer review and regulatory rulemaking. A substantial weight of toxicological or epidemiological evidence supports the decision to list a chemical as a recognized health hazard under Proposition 65. Stakeholders that believe a chemical does not cause a recognized health effect have the opportunity to argue that the evidence does not support identifying the chemical as a hazard. If a chemical is listed under Proposition 65, such arguments failed to convince neutral scientific and regulatory experts.

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 resolved conclusively.

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.