Scorecard does not cover all major environmental problems, sources of pollution, or potential exposures to toxic chemicals. Our profiles are limited to environmental issues tracked by authoritative national data sources. There are many gaps in the coverage of national regulatory programs, leading to gaps in our understanding of local environmental problems. Scorecard is committed to publishing the most current environmental data available, and is regularly revised as its data sources are updated.

Each major section of Scorecard includes specific caveats about the data and methods used to produce Scorecard reports:

Scorecard ranks geographic areas and companies using various environmental attributes. Air pollution rankings can be based on estimated health risks, monitored exposures or reported emissions. Toxic chemical release rankings can be based on the raw data companies report to the Toxic Release Inventory (e.g., total environmental releases), or using information about the health hazards of reported releases (e.g., releases of recognized carcinogens to air). Animal waste rankings are based on estimates of waste generation. The rankings are relative: they tell you how a facility or area ranks compared to other facilities or areas. The rankings do not tell you whether the amount of pollution in your area is safe or unsafe.

Scorecard uses information from scientific sources and regulatory agencies to provide listings of the chemicals that can cause cancer, harm the immune system, contribute to birth defects, or lead to nine other types of health effects. Chemicals with health hazards that are widely recognized by authoritative scientific organizations are listed separately from the chemicals whose hazards are only suspected on the basis of more limited data. Scorecard uses the State of California's official list of chemicals with known toxic properties as its source for the chemicals that are recognized to cause cancer, reproductive toxicity, and/or developmental toxicity. Scorecard's lists of suspected health hazards are based on an extensive review of medical textbooks, scientific literature, and regulatory agency sources.

Some Scorecard reports provide risk scores or health risk estimates for toxic chemicals. All risk statements are based on a screening-level assessment of potential health risks and are subject to important uncertainties. Scorecard's risk estimates are calculations based on models: they are useful for ranking purposes, but are not necessarily predictive of any actual individual's risk of getting cancer or other diseases.

For a particular person suffering from a particular health effect, it is often very difficult to tell whether environmental pollution was the cause or one of the causes. Scorecard's information should not be considered by anyone as medical advice and it is not a substitute for care by a licensed health professional.