What would be less alarming and more accurate would be a statement that also included the sentence: "When using this product in the manner for which it is designed and instructions are given, there is no risk of harm." However, the threat of legal shenanigans seems ever more often to make simple common sense to be legally inadequate.
I hear where you're coming from, but on both technical and medical grounds I can't agree with the statement you've proposed.
There is a good reason that such a statement is legally inadequate -- it's because it is not known and cannot be known. It simply cannot be proved, especially to the degree of certainty that you've put into that sentence. You would need a sample size that exceeds the number of actual users of the product, follow them for decades, control for all other confounding variables,
and match them with a control group that does not use these chemicals at all.
So
maybe they're 100% safe when used as described by the manufacturer. Or
maybe there is a relative risk of 1.5 or 2.1 or whatever for renal cell carcinoma in people who exceed a certain threshhold of exposure (again, very difficult to define at low, sub-occupational exposure levels).
Many organic solvents have been associated with cancers. The Marlene cleaner in the Marshall oil set contains trichloroethylene, which is a pretty famous one (and probably the carcinogen to which the warning refers). It's
probably unlikely that a typical hobbyist will be at increased risk for cancer from this chemical, and there are other more important exposures (like filling your car) but again, it's hard to know.
Here is the abstract from a recent review on trichloroethylene:
Environmental Health Perspect. 2006 Sep;114(9):1471-8.
Scott CS, Chiu WA
National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, USA.
A large body of epidemiologic evidence exists for exploring causal associations between cancer and trichloroethylene (TCE) exposure. The U.S. Environmental Protection Agency 2001 draft TCE health risk assessment concluded that epidemiologic studies, on the whole, support associations between TCE exposure and excess risk of kidney cancer, liver cancer, and lymphomas, and, to a lesser extent, cervical cancer and prostate cancer. As part of a mini-monograph on key issues in the health risk assessment of TCE, this article reviews recently published scientific literature examining cancer and TCE exposure and identifies four issues that are key to interpreting the larger body of epidemiologic evidence: a) relative sensitivity of cancer incidence and mortality data ; b) different classifications of lymphomas, including non-Hodgkin lymphoma ; c) differences in data and methods for assigning TCE exposure status ; and d) different methods employed for causal inferences, including statistical or meta-analysis approaches. The recent epidemiologic studies substantially expand the epidemiologic database, with seven new studies available on kidney cancer and somewhat fewer studies available that examine possible associations at other sites. Overall, recently published studies appear to provide further support for the kidney, liver, and lymphatic systems as targets of TCE toxicity, suggesting, as do previous studies, modestly elevated (typically 1.5-2.0) site-specific relative risks, given exposure conditions in these studies. However, a number of challenging issues need to be considered before drawing causal conclusions about TCE exposure and cancer from these data.
So I'd avoid contact with bare skin and use it in a well ventilated area. Seems pretty safe and easy to me.
As for why the warning is there, it's because there is indeed a body of evidence to support its truth. It's not quite as blisteringly obvious as say smoking and lung cancer, but the warnings are on cigarette packs for a reason and the warnings are on other harmful products for a reason as well.
Perhaps the bottom line is avoiding legal liability. But at the same time if there
is a risk of harm to the consumer, then as a consumer you want the opportunity to make an informed choice. For example, if you have chronic hepatitis B, then it's really in your best interest to avoid a second cause of hepatocellular carcinoma. It's easy to be cynical about our very litigious culture in the USA, and being in medicine I'm as cynical as anyone about it. But think as a consumer advocate for a second, and you'll see that informed decision-making really is an expectation that we all share, and if there is a
known risk inherent in some product, we have the right to know.
