As millions of us who play and work under the bright sun dutifully slather our bare skin with creams, oils and sprays, consumer safety activists continue to blast the government for failing to ensure the safety of these sunscreens.

The latest target of concern is the use by sunscreen manufacturers of nanosized particles of titanium dioxide and zinc oxide. A new report based on several preliminary studies says these atom-sized additives have the potential to cause serious harm.

That follows last week’s report that the Food and Drug Administration has known for a decade that almost half of the most popular sunscreens contain an ingredient that may actually accelerate the growth of skin cancer cells.

France, Germany, the U.K. and the European Parliament have moved rapidly to require everything from safety testing and mandatory labeling of nanoparticles to even the outright ban of these engineered chemical creations in many sunscreen and cosmetic products. Nothing of the kind is happening in the United States, Friends of the Earth says in a report issued today. .

“Nanosunscreens have the potential to cause serious human and environmental harm, but there is nothing stopping companies from selling them,” says the report by the international environmental and public health advocates.

And consumers are pretty much on their own when it comes to determining what’s safe to slather on their skin. Labeling is often inadequate or inaccurate. And not even the Consumer Safety Protection Commission, which ensures the safety of the items that Americans buy, is stepping up for sunscreen shoppers.

“It’s not our responsibility. Sunscreen safety is FDA’s job,” says Alexander Filip, deputy director of public affairs for the commission. But, he added: “Our chairman has publicly addressed industry groups warning them about use of nanomaterials without notifying us or their customers.”

Studies Still Preliminary

Today’s report calls the use of nanoparticles of titanium dioxide and zinc oxide a “risk without benefit.” It examines six studies on the health implications of manufactured nanomaterials used in sunscreens.

The studies, which raised some concerns in the public health community, are all peer-reviewed and have been published in international scientific journals. But the authors of almost all the work stress that their studies are preliminary and that more research is needed.

Friends of the Earth says the studies indicate that:

Zinc oxide nanoparticles can kill important brain stem cells in mice and that nano-titanium dioxide injected into pregnant mice produced gene changes.

Nanosized zinc oxide is toxic to colon cells even in small amounts.

Autistic disorders, epilepsy and Alzheimer’s disease have been linked to nano-titanium dioxide.

The zinc used in nano-sunscreens can penetrate healthy human skin and potentially reach the blood stream and urine of humans.

Nanoparticles also can cross into human placentas from mothers to unborn fetuses.

“Consumers need to know that manufactured nanoscale zinc and titanium oxides are not the only choice and are not necessarily the most effective or safest choice for sun protection,” the report cautions.