In June 2007, the Environmental Working Group (EWG) released a study showing that over 650 sunscreen products used in the United States are either ineffective or cause harmful side effects. That represents 83% of the 785 name-brand sunscreens with SPF ratings or 15 or higher that the EWG analyzed.A full 12% of all of the sunscreens analyzed by the EWG protect only from sunburn (ultraviolet B or UVB radiation), containing no ingredients that protect from skin damage and aging, immune system problems, and potential skin cancer (ultraviolet A or UVA radiation).According to the report, many of the problems derive from the complex formulation of newer sunscreens. For example, some sunscreen chemicals can break down when they are exposed to sunlight so those products must be formulated with stabilizers. The EWG noted that 54% of the products it examined contain ingredients that may be unstable alone or in combination; this raises questions about whether the products last as long as their label claims they do.Just 17% of the products analyzed for the study were found to be safe and effective, blocking both UVA and UVB radiation, remaining stable in sunlight, and containing few or no ingredients with significant known or suspected health hazards. Many of these products contain micronized and nano-scale zinc oxide and titanium dioxide, which provide strong UVA protection. Repeated studies have found that these ingredients do not penetrate healthy skin, indicating that consumers' exposures would be minimal. However, studies on other nano-scale materials have raised concerns about their toxic properties. These particles are so small that they can penetrate the skin, presenting as yet unknown health risks.As of mid 2007, the U.S. Food & Drug Administration (FDA) has failed to approve several effective UVA filters available in Europe that could replace these potentially dangerous nano-scale ingredients. So far, the FDA has approved just 17 sunscreen chemicals for use in the U.S., while there are at least 29 such chemicals approved for use in the E.U.