Psssst, summer’s coming, so it’s time to study up on sunscreens.

There are debates swirling about the health impacts of sunscreens. What’s up with that? Are some safer than others? How should sunscreens be used? Or should we just stick to the shade?

The key is balance and, importantly, avoiding the wrong sunscreens.

Plans vary. But fortunately there are resources and tips to help.

Smart sunning requires finding that level of exposure that gives our body the sun-derived Vitamin D it needs while avoiding three types of skin cancer: melanoma, squamous cell and basal cell.

First off, we have to recognize that vitamin D is a key nutrient the body needs to fight a variety of diseases such as diabetes, rheumatoid arthritis, high blood pressure and some forms of cancers. And experts say a surprising number of people lack Vitamin D. So, generally speaking (and there are always exceptions) we do need some sun … sans sunscreen.

Calculated Sun Time

With that in mind, what are the sunscreen rules?

Michael F. Holick, Ph.D., M.D., has been researching this and discusses it in his book, The UV Advantage. Holick, who’s also professor of medicine, physiology and biophysics at Boston University School of Medicine, says more than 120 peer-reviewed studies demonstrate that moderate exposure to UV (that’s ultraviolet) light will give the body the vitamin D it needs without significant skin damage.

Holick says that slathering SPF 15 sunscreen all over your body (about one ounce) prevents its ability to make vitamin D by 95 percent. For that reason, he says everyone needs a little unprotected time in the sun, depending on the latitude, time of day, season and degree of skin pigmentation. His book offers tables for knowing how much to get but, he says, there’s a rule of thumb: Typically for very light skin Caucasians — who will get mild pinkness after a half-hour in the sun — he recommends only a fraction of that, some five to 12 minutes, two to three times a week. After that, with a base tan built up, he says, the fair skinned can stay in the sun about twice that time. Then bring on the hats and sunscreen. Those of you with darker skin extrapolate accordingly (or buy his book).

Toni Bark, M.D., medical director for the Center for Disease Prevention and Reversal in Chicago, recommends if you’re going to be in the sun, start your day by putting antioxidant vitamin lotions on your exposed skin. “Many studies have shown vitamins C and E to be protective against cellular damage caused by either the sun or free radicals in general,” she says.

As an avid hiker and skier of sunny slopes, the doctor, 45, swears by her personal program that includes, first thing in the morning, using a lotion with 20 percent vitamin C if she’s going to be outside. With that, she mixes pure vitamin E oil, putting it on the parts of her body that will be exposed to sun. She’ll do her time in the sun without sunscreen and then apply it. All the while, giving her body the protective “force field” of the antioxidants, vitamins C and E.

Absorb or Block Those Rays?

When shopping for a sunscreen, experts say consumers should buy broad-spectrum products that block both UVB and UVA rays. And, this is where it starts to get dicey … know your sunscreens!

Importantly, Bark says, sunscreens are lumped into two categories, the chemical types and the physical or mechanical types. Chemical sunscreens, she says, generally absorb UVB radiation, the so-called “burning rays” of the sun and then disperse that energy through chemical reactions generating those maverick “free radicals” that rust our cells from the inside out. “There has been a growing body of evidence that this free radical formation causes DNA damage and or breakage,” she advises. (Some sunscreen brands are better than others; we’ll get to that.)

In contrast, says Bark, physical or mechanical sunscreens — notably called sun blocks — come in the old-fashioned form of titanium dioxide and zinc oxide, white creams that reflect radiation rather than absorb it. As founder of Plan-It-Green and Apothecare, companies that sell healthy, enviro-friendly products, the physical sunscreens are Bark’s favorite form of sun protection.

Even so, the problem for sunscreen makers is that the white stuff wears like clown make-up (not always a popular look) so companies have shrunk the molecules to eliminate the problem. “But this was done at the expense of toxicity,” Bark notes, “and these smaller-molecule physical sunscreens have been shown to cause some DNA damage as well.” So if you use the mechanical sun blocks, maybe start a beach trend and wear the Bozo make-up (she says it does come in different fun colors!).

The Dark Side of Sunscreens

Manufacturers use a confusing mix of chemicals to make sunscreens. But the Environmental Working Group (EWG), a frequently cited watchdog organization, has authored a report to help us know what’s, ahem, getting under our skin.

In a remarkable interactive database, entitled Skin Deep (see info box), EWG offers a safety assessment of 166 sunscreens and tanning oils. The report, which contains info about specific products, found that:

• 80 of the reviewed products may pose cancer risks.
• 11 contain ingredients that damage the skin and may increase risk of skin cancer.
• 52 products contain ingredients that may contain impurities linked to breast cancer.

To help consumers get wise, the EWG has also flagged 10 products it says carry the highest potential danger. Topping the list is “Murad APS Oil-Free Sunblock Sheer Tint” containing a cocktail of questionable chemicals, including triethanolamine, which EWG says may form cancer-causing nitrosamines when rubbed into the skin. In fact, six of the 10 products identified as those “you may want to avoid” contain triethanolamine, including Banana Boat and Coppertone products marketed for kids.

Complicating matters, the report says many sunscreens contain chemicals that have not been assessed for safety. For example, the Banana Boat product, “Baby Magic Sunblock Spray, SPF 48” ranked high for potential health dangers, containing 16 unstudied chemicals.

So know what you’re getting and seek out the least questionable products. The EWG helps by listing what it says are “Better Choices.” Ironically, both Coppertone (Sport Sunblock Gel, SPF 30) and Banana Boat (Protective Tanning Oil Sunscreen, SPF 15) have products on this list as well. Among natural-products companies, Jason and the French company Mustela make the grade.

It’s important to remember that health data is very limited on many of the chemicals used in sunscreens (and other personal care products). Think of groups like EWG as erring on the side of caution, calling attention to the fact that ill-understood and potentially harmful chemicals may present cumulative health impacts after consistent, long-term use—not single applications.

Kelly Hearn writes from and suns himself in Buenos Aires, Argentina.

A study of infants in intensive care finds a substance used in medical supplies that causes testicular damage in animals.

A Harvard study of babies in hospital intensive care units has found new evidence of high levels of a hormone-altering chemical in newborns treated with plastic medical devices.

Some intravenous lines, blood bags, feeding tubes and a variety of other medical equipment contain the chemical, a phthalate called DEHP, which is widely used to make vinyl soft and flexible. In a study conducted at two hospitals in the Boston area, babies undergoing the most intensive care with the plastic devices, particularly endotracheal tubes and umbilical vein catheters, had five times more DEHP in their bodies than babies who were not treated with them.

The findings add to a growing body of research that has found that phthalates, also used in cosmetics, are ubiquitous in human bodies and has raised questions about their safety, particularly for baby boys.

The scientists at the Harvard School of Public Health did not examine the effects on the study’s 54 critically ill or premature babies at the neonatal intensive care units. But in laboratory tests on animals, DEHP blocks testosterone and causes testicular damage. Last month, scientists found that male babies exposed to four phthalates in the womb were born with slightly altered genitals, although DEHP, the type found in medical equipment, was not one of them.

Since 2002, the Food and Drug Administration has advised hospitals to limit use of medical devices that contain phthalates. But the agency has not banned them and many neonatal units still use them despite the availability of alternatives.

In the study, significantly lower phthalate levels were found in the urine of babies at the hospital that had switched to some DEHP-free devices.

“The more products being used, the higher the level of [phthalate metabolites] found in urine,” said Howard Hu, a professor of occupational and environmental medicine who was the lead researcher in the study, which was published online Wednesday in the journal Environmental Health Perspectives.

“Our study not only demonstrates that [neonatal intensive care] infants … are exposed to demonstrably high levels of DEHP, but we have also clearly linked the intensity of DEHP product use with the amount of DEHP that enters infants’ bodies,” Hu said.

Antonia Calafat, a researcher with the Centers for Disease Control and Prevention and a co-author of the study, said the amounts in the most highly exposed infants were 17 times higher than the amounts found in the general population of U.S. children.

Representatives of the American Chemistry Council, a trade group for the chemical industry, said Wednesday that the new study “states the obvious — newborns who receive intensive care, perhaps to save their lives, have measured phthalate levels above the average.”

The industry officials stressed that the levels in the newborns were lower than the doses that showed no effect on lab animals.

The study authors agreed, although they did not include such comparisons in their report because of differences between their research and the animal studies. They said it was possible that some babies undergoing very intensive or lengthy treatment with the devices had doses higher than those that harmed the rats.

“Based on our results and what we know about the toxicity of DEHP from studies in laboratory animals, we need to better understand whether there are potential health risks” to babies in hospitals, said co-author Russ Hauser, a Harvard associate professor of occupational health.

Health Care Without Harm, a coalition of 435 health and environmental groups in 53 countries, urged hospitals on Wednesday to immediately stop using the vinyl devices and switch to ones that are DEHP-free.

The FDA recommends that hospitals substitute non-phthalate medical equipment when treating infant boys or pregnant women carrying boys. Although adults are also exposed to phthalates from medical equipment, the greatest risk is for baby boys and male fetuses, whose reproductive organs are developing.

Baxter International Inc., one of the world’s leading producers of medical devices, would not comment Wednesday on the new study. But the company’s website said that vinyl containing DEHP has been used safely in medical equipment for 40 years and that it remained the “material of choice” for many important devices because of its flexibility. The company emphasized that there was no evidence of harm to human beings.

“When DEHP-plasticized PVC provides the best overall performance, Baxter will continue to use it,” said the company’s position paper on the topic.

Valerie Briscoe, a neonatal clinical nurse specialist at John Muir Medical Center in Walnut Creek, Calif., said her hospital already eliminated all DEHP products in its neonatal unit.

“This study confirms my concern that [hospitals] should really move forward on this,” Briscoe said.

Briscoe said that the switch in equipment was made “with no substantial cost impact to the hospital” and no adverse effects on the babies’ treatments.

“Ninety-nine percent of the products have alternatives out there,” she said.

Kaiser Permanente also has phased out the devices in neonatal units, and is working to find substitutes for other uses, such as building materials and carpeting.

DEHP is the highest volume phthalate in production, used in a variety of PVC products such as flooring, toys, food containers and automobile parts.

Other phthalates are used as ingredients in nail polish, fragrances and other beauty products.

WSU findings show that disorders can be passed on without genetic mutations

It’s just a study involving a few rats with fertility problems in Pullman, but the findings could lead to fundamental changes in how we look at environmental toxins, cancer, heritable diseases, genetics and the basics of evolutionary biology.

If a pregnant woman is exposed to a pesticide at the wrong time, the study suggests, her children, grandchildren and the rest of her descendants could inherit the damage and diseases caused by the toxin — even if it doesn’t involve a genetic mutation.

“As so often happens in science, we just stumbled onto this,” said Dr. Michael Skinner, director of the center for reproductive biology at Washington State University.

Skinner’s team at WSU and colleagues from several other universities report in today’s Science magazine on what they believe is the first demonstration and explanation of how a toxin-induced disorder in a pregnant female can be passed on to children and succeeding generations without changes in her genetic code, or DNA.

“We were quite surprised … we’ve been sitting on this for a few years,” said Skinner, who is expected to present his findings today at a scientific meeting in San Diego.

The report in Science, entitled “Epigenetic Transgenerational Actions of Endocrine Disruptors and Male Fertility,” also sounds like an attempt to avoid attention. That’s unlikely to work. The findings prompt serious and, in some cases, disturbing questions about a number of basic assumptions in biology.

The standard view of heritable disease is that for any disorder or disease to be inherited, a gene must go bad (mutate) and that gene must get passed on to the offspring.

What Skinner and his colleagues did is show that exposing a pregnant rat to high doses of a class of pesticides known as “endocrine disruptors” causes an inherited reproductive disorder in male rats that is passed on without any genetic mutation.

It’s not genetic change; it’s an “epigenetic” change. Epigenetics is a relatively new field of science that refers to modifying DNA without mutations in the genes.

“It’s not a change in the DNA sequence,” Skinner explained. “It’s a chemical modification of the DNA.”

Scientists have known for years about these changes to DNA that can modify genes’ behavior without directly altering them.

One form of epigenetic change is natural. Every cell in the body contains the entire genetic code. But brain cells must use only the genes needed in the brain, for example, and kidney cells should activate only the genes needed for renal function.

Cells commonly switch on and off gene behavior by attaching small molecules known as methyl groups to specific sections of DNA. The attachment and detachment of methyl groups is also an important process in fetal development of the male testes and female ovaries — which is where Skinner got started on this.

But the common wisdom has been that any artificially induced epigenetic modifications will remain as an isolated change in an individual. Because no genes get altered, the changes cannot be passed on.

“We showed that they can be,” Skinner said.

The experiment got its start four years ago by accident. His lab was studying testes development in fetal rats, using a fungicide used in vineyards (vinclozin) and a common pesticide (methoxychlor) to disrupt the process. A researcher inadvertently allowed two of the exposed rats to breed, so the scientists figured they’d just see what happened.

The male in the breeding pair was born with a low sperm count and other disorders because of the mother’s exposure to toxins. No surprise. But the male offspring of the pair also had these problems, as did the next two generations of male rats.

“I couldn’t explain it,” Skinner. This wasn’t supposed to happen.

The scientists didn’t tell anyone about their finding and continued, for the next two years, to confirm that it was real and to find an explanation. Eventually, they documented that a toxin-induced attachment of methyl groups to DNA in the mother rat was being passed on to offspring.

“In human terms, this would mean if your great grandmother was exposed to an environmental toxin at a critical point in her pregnancy, you may have inherited the disease,” Skinner said.

While the study was focused on a heritable disorder of reproduction in rats, he said there’s every reason to believe this can happen for other diseases — such as cancer.

“There has been this speculation that the increased rates of some cancers may be due to environmental factors, but they’ve never been able to describe a mechanism to explain this,” Skinner said.

The findings also suggest a reconsideration of one of the basic tenets of evolutionary biology — that evolution proceeds by random genetic change.

The standard view is that the environment has no direct influence, except in how it may favor or discriminate against the creatures with the latest genetic mutations.

The WSU study, Skinner said, suggests the possibility that environmental factors such as toxins may also directly cause heritable changes in creatures. “Epigenetics may be just as important as genetics in evolution,” he said.