Just as summer begins and people are stocking up on sunscreen, a new report is raising questions about the safety and effectiveness of many brands. But the truth behind those attention-grabbing headlines is more complicated.

The research, conducted by a nonprofit advocacy group that verifies sunscreens with its own seal, looked at more than 2,200 sunscreens and found that just 498 met its high bar for safety and effectiveness. While the group, called the Environmental Working Group (EWG), raises valid concerns about certain chemical ingredients, which some studies link to health risks in mice, experts caution that the report leaves out key research findings. “They used a fraction of the literature out there to determine safety,” said Adam Friedman, MD a dermatologist at The George Washington University School of Medicine & Health Sciences in Washington, D.C.

Two JAMA studies cited by the report, for instance, found that various UV filters — the chemicals in sunscreens that absorb or block sunlight — could be detected in people’s blood after repeated application, but neither study showed effects on the body, Friedman said. “The reality is, whether it be human safety or even environmental safety, there are tons of studies showing the safety of the very few organic and mineral filters that we have,” said Friedman. “Also there’s tons of longitudinal data showing that the sunscreens we have, the ingredients we have, can protect against accelerated skin aging and skin cancer.”

In the U.S., 1 in 5 people will develop skin cancer by age 70, and 20 people per day die of melanoma, the deadliest form of skin cancer. The sun releases a full spectrum of ultraviolet (UV) radiation, a form of energy that’s part of the electromagnetic spectrum. UVB is a type of UV radiation, and so is UVA. UVB rays are shorter and have a greater effect on sunburn. They can also damage the skin’s DNA, leading to skin cancer.

UVA rays are longer and penetrate deeper into the skin, causing skin aging. They also contribute to sunburn, skin cancers, and rashes, said Zakia Rahman, MD, clinical professor of dermatology at Stanford. Broad-spectrum sunscreens protect you against both UVB and — to an extent — UVA rays. However, “they’re not great at UVA,” Friedman said. “They’re sufficient from an FDA perspective, but they’re not great. We have very few UVA filters.”

“They work in different ways, but they still achieve the same effect,” said Syril Keena Que, MD, MPH, professor of dermatology at the Indiana University School of Medicine in Indianapolis.