HEALTH EFFECTS|Member - Class Hazard Identification Rules

Some of the toxic chemicals included in Scorecard are actually classes of related chemicals (e.g., arsenic compounds or polychlorinated biphenyls). Other Scorecard chemicals are members of classes (e.g., lead nitrate is a member of the class of lead compounds). Scorecard indicates whether substances are classes or members of classes in the Links section of every Chemical Profile. Tracking the class and member status of toxic substances is important for correctly identifying chemical hazards.

Scorecard's authoritative source for identifying recognized health hazards is Proposition 65. Like most hazard identification references, Proposition 65 identifies both chemical classes and specific members as recognized carcinogens, developmental and reproductive toxicants. For example, cadmium and cadmium compounds are identified as carcinogens. This hazard identification extends to all members of the class of cadmium compounds, although a detailed listing of specific cadmium compounds is not provided.

To ensure that all members of classes that are recognized hazards inherit the identification assigned to their class, Scorecard is programmed to utilize the following decision rule:

1) If a class has been assigned a recognized health effect, all members of that class should also be assigned that recognized health effect. Recognized -> recognized hazard identification inheritance is transferred down through all intervening subclasses to all constituent members.

In some cases, Proposition 65 identifies the health hazards of specific members of a class of compounds, but is silent about the class. To determine the type of hazard that should be assigned to a class based on its members, Scorecard utilizes the following decision rules:

2) If all members of a class have been assigned a recognized health effect, that class should be assigned that recognized health effect.

3) If any member of a class has been assigned a recognized health effect, that class should be assigned that suspect health effect. Recognized->Suspect hazard identification inheritance is transferred up through all intervening subclasses to the most inclusive class.

P65-MC is the reference citation provided for any chemical with hazard identification based on these rules.

In many cases, suspect health hazards have been identified for chemicals that are classes or members. Because these hazard identifications are more uncertain than the authoritative determinations made under Proposition 65, it was considered inappropriate to assume all members of a class should inherit a suspect health effect assigned to that class. Scorecard also does not transfer suspect health hazards to a class from a member (even if there is consistency in suspect health effects across members).

Note that these decision rules are very strict about when it is appropriate to assign member hazard identifications to a class. This is done to preserve the scientific defensibility of Environmental Defense's hazard identification project.

Users are encouraged to examine the suspect health effects assigned to classes and members via the Links section of Chemical Profiles. Even if a certain health effect is not directly associated with a TRI category like diisocyanates (EDF-067), for example, it is possible to examine the profiles of members of this class and learn that several are suspect immunotoxicants and skin and sense organ toxicants.