The HPV program ignores human exposures, and demands testing, whether humans could potentially be exposed or not. It must be remembered that the HPV program's goal is not to perform a thorough toxicity battery on any chemical. Rather it is to determine whether crude screening information exists. In this situation, animal tests are often so inaccurate that they do more harm than good. The inability of animals to replicate human exposure results leaves plenty of room for interpretation and disagreement.
Tobacco presents a tragic example.
The link between cigarette smoking and lung cancer is abundantly clear from human studies. However, animal tests muddied the waters. Tobacco tar painted on animals' skin led to tumor production, while animals forced to inhale tobacco smoke in one study after another simply failed to develop bronchogenic carcinoma. The tobacco industry was able to argue that since humans inhale tobacco smoke, rather than paint it on their skin, it did not appear to be a dangerous substance. Far from helping public health programs, these tests worked to the tobacco industry's advantage.