At long last, microbeads are on their way out. In December, Congress banned the tiny bits of plastic found in body scrubs, face washes, toothpaste, and more. An estimated 8 trillion microbeads slip through bathroom drains in the US and pass into the country’s aquatic habitats each day, according to a September study published in Environmental Science and Technology. The tiny plastic balls pollute the world’s lakes and oceans and wind up in the bellies of fish, which could in turn pass on chemicals to the people and wildlife who consume them.

The ban, which goes into effect in 2017, is certainly good news. But the very existence of microbeads highlights a larger problem in the cosmetics industry. Lots of the ingredients in our products—even the “natural ones”—eventually make their way into the environment. Yet there’s a lot we don’t know about how those ingredients affect nature. That means people hoping to purchase truly earth-friendly cosmetics have their work cut out for them.

One thing is clear: conscientious consumers can’t rely on the promises of green packaging. Microbeads often pop up even in cosmetics that bill themselves as environmentally friendly—including products from Aveeno Active Naturals, Hempz, and Tree Hut.

The problem is far from specific to microbeads. Take the antibacterial agent triclosan, found in many different brands, including those with names like “Tea Tree Therapy” and “Naturade.” The lab-made chemical is washed down drains into water systems, and ultimately, the bodies of fish. Once ingested, the chemical makes fish sluggish, according to researchers at the University of California, Davis and the University of Colorado—even in situations where a fish is threatened by a predator.

Cosmetic ingredients actively favored by environmental groups aren’t always better for the planet either. Many earth-friendly types tout mineral sunscreen, for example, which contains zinc and titanium to physically repel sunlight. This kind of sunscreen is billed as a healthier alternative to “chemical sunscreens,” which some environmental groups worry could enter the bloodstream and act like hormones in humans, disrupting the reproductive cycle. (Research has shown that this is probably only possible if you slather on sunscreen all day, every day for your whole life.)

But the small nano-zinc formulas in mineral sunscreen may prevent sea urchin embryos from fully developing, according to a paper published last spring by Gary Cherr, a marine toxicologist at the University of California, Davis.

The zinc is “not terribly toxic at trace levels,” Cherr tells Quartz. But he thinks that when thousands of people are on a crowded beach, mineral sunscreen could eventually reach levels harmful for urchins.

Yet research on the effects of chemical sunscreens suggest they may have a similar effect on coral reef systems. And preliminary work in Cherr’s lab suggests that in fact, all sunscreens could have a negative effect on sea urchins.

This is part of the problem with natural cosmetics. They traffic in the idea that if we avoid certain ingredients, we’ll be ethically in the clear.

“This is kind of the classic tradeoff as we develop technology to protect ourselves,” says Cherr, who personally continues to use sunscreen despite what his studies say.

Cosmetic ingredients that travel through the air can also build up in–and potentially affect–the environment. Cyclomethicone, a kind of silicone, is used in products to make hair look shiny and skin feel smooth. When we spray it on our heads or slather it on our bodies, it evaporates into the air, which carries it out of our houses and into the world.

Last year, scientists at the Institute of Environmental Assessment and Water Research in Spain reported finding traces of methlysiloxane, the chemical unit that composes cyclomethicone, in soil samples from Antarctica. This went against scientists’ previous understanding that methylsiloxane simply hung in the atmosphere. Methylsiloxanes have also been found in soil and fish in rural areas of North America and Europe.

It will take further studies to verify the claim that methylsiloxanes are infiltrating the farthest reaches of the earth. Some scientists thought that the Antarctic samples might have been contaminated. Moreover, it’s unclear what, if any, ill effects methylsiloxanes have on the environment. The Environmental Protection Agency is currently assessing the effects of one methylsiloxane compound.

What is clear is that our chemical technology is already out in the environment—and once it’s released, where it goes is largely beyond our control.

The ban on microbeads is a solution to an uncommonly clear-cut problem. But in general, it’s hard to reach a clear-cut conclusion about which products are harmful to the environment. The risks vary depending on the circumstances and the concentrations in which a given ingredient is used.

Most ingredients in our cosmetics aren’t categorically dangerous or safe. Given the abundance of grey areas, consumers who really want to do the most they can for the environment have a boring but simple solution: just buy fewer products.