In the case of nuclear accidents, for example, individual governments decide, in the light of their interpretation of a range of evidence, at what level of radioactive contamination pasture land, drinking water, milk, eggs, vegetables and fish are to be banned as unfit for consumption, firstly by humans and secondly by livestock. Different countries, and even different local authorities within countries, have different criteria. Some have none at all. Sometimes the criteria changes and what was once acceptable may become dangerous in the future. Some may apply rigorous criteria to ban suspect foodstuffs, but may then apply very relaxed criteria to assess the risk from foodstuffs imported from neighbouring countries where very permissive criteria, if any, are applied.
For 71 percent of the 3,000 highest-volume chemicals in the U.S. economy no human health-effect screening has ever been conducted. A 1984 report released by the National Academy of Sciences' National Research Council documented a lack of "even minimal" health screening tests for 78 percent of high-production-volume chemicals in the U.S. In July of 1997, the Environmental Defense Fund released a study entitled "Toxic Ignorance" that pointed to the lack of improvement in screening over the last 13 years. In conjunction with the report's release, the EDF called for commitments from the chief executive officers of the 100 top chemical manufacturers in the U.S. to complete preliminary health screening tests on each company's top-selling chemicals before the year 2000, and disclose the results to the public. According to the EDF study, the testing requested would cost between 1/10 of a cent to 2/3 of a cent per dollar of profit for the top 100 US companies, which made profits of $29.4 billion last year on $230.5 billion of chemical sales. In the meantime, the effects of these chemicals on wildlife, and on humans, remain unknown.
According to the British Toxicological Society, there is "no reliable method" to extrapolate data from laboratory animals to human beings.
The regulatory system in the USA is rigged to benefit the chemical manufacturers while keeping the general public in a dangerous state of ignorance. Very few Americans, for example, realize that the federal government does not screen chemicals for safety before they go on to the market. It is up to the chemical manufacturers themselves to determine whether a product poses a substantial risk to health or the environment. Only a fraction of the tens of thousands of chemical compounds on the market today have been examined for safety. Those examinations, for the most part, were conducted only after specific questions were raised about a specific product.
Once a chemical is on the market, it is incredibly difficult to get it off. The chemical companies have nearly perfected the art of shielding products from the interference of government regulators, public interest groups and private citizens who have been grievously harmed.