Several studies have been conducted in recent years to investigate what role, if any, static magnetic fields may play in health and healing. Unbiased studies of magnetic therapy are problematic, since magnetisation can be easily detected, for instance, by the attraction forces on ferrous (iron-containing) objects; because of this, effective blinding of studies (where neither patients nor assessors know who is receiving treatment versus placebo) is difficult. Incomplete or insufficient blinding tends to exaggerate treatment effects, particularly where any such effects are small. Health claims regarding longevity and cancer treatment are implausible and unsupported by any research. More mundane health claims, most commonly about anecdotal pain relief, also lack any credible proposed mechanism and clinical research is not promising. The American Cancer Society states that "available scientific evidence does not support these claims". According to the National Center for Complementary and Integrative Health, studies of magnetic jewelry have not shown demonstrable effects on pain, nerve function, cell growth or blood flow. A 2008 systematic review of magnet therapy for all indications found insufficient evidence to determine whether magnet therapy is effective for pain relief, as did 2012 reviews focused on osteoarthritis and rheumatoid arthritis. These reviews found that the data was either inconclusive or did not support a significant effect of magnet therapy. They also raised concerns about allocation concealment, small sample sizes, inadequate blinding, and heterogeneity of results, some of which may have biased results. Safety These devices are generally considered safe in themselves, though there can be significant financial and opportunity costs to magnet therapy, especially when treatment or diagnosis are avoided or delayed. Use is not recommended with pacemakers, insulin pumps, and other devices that may be negatively affected by magnetic fields. Reception The worldwide magnet therapy industry totals sales of over a billion dollars per year, including $300 million per year in the United States alone. A 2002 U.S. National Science Foundation report on public attitudes and understanding of science noted that magnet therapy is "not at all scientific." A number of vendors make unsupported claims about magnet therapy by using pseudoscientific and new-age language. Such claims are unsupported by the results of scientific and clinical studies. Legal regulations Marketing of any therapy as effective treatment for any condition is heavily restricted by law in many jurisdictions unless all such claims are scientifically validated. In the United States, for example, U.S. Food and Drug Administration regulations