Do you know what’s in your beauty products? The answer may be more complicated than you think: Labeling is tricky, with many cosmetics featuring ingredient lists that require a PhD in chemistry to decipher, or packaging that touts simple but unregulated claims like “non-toxic,” “chemical free,” or “clean.”

“I’m more comfortable with ‘clean’ than any other definitive claim out there,” says the Environmental Wellness Group’s Director of Healthy Living Science, Nneka Leiba, M.Phil., MPH. “Nothing is completely ‘non-toxic,’ not even water. But ‘clean’ at least acknowledges the movement to have clearer, safer products and the education that offers.” By all accounts, it’s a movement that is gaining momentum. The Personal Care Products Safety Act bill, which would grant the FDA more authority over cosmetics, requiring companies to ensure their products are safe before hitting shelves, was re-introduced earlier this year and has bi-partisan support. Until then, says Leiba, “it’s up to the brands and the consumers to demand transparency and a phasing out of chemicals of concern."

So where does Westman Atelier stand when it comes to this important conversation?

When we created our clean makeup line, we wanted to achieve two things: Skin-nourishing makeup that would target specific issues like rosacea with ingredients formulated at proven efficacy levels—and products that were safe and responsible. With the help of independent green chemists and industry advisors, we are committed to including the highest amount of natural, plant-based active ingredients possible without disrupting a product's formulation and performance. That means when we do use a synthetic, it has been thoroughly safety vetted, from both a human and environmental standpoint, and transparently explained.

To make things crystal clear, we’ve also drawn up an ingredient "no" list. (Stay tuned for the complete "What's In" glossary, coming soon.) Here are the 11 substances that will never appear in our formulas and why. 

Parabens, act as preservatives in makeup like eye shadow and have been linked to reproductive health risks in animals. But they’re also endocrine disruptors, a group of chemicals that impacts our hormone system, which guides almost everything in the body, from growth to reproductive development. The most commonly used types in personal care products to look for on labels include: methyl-, ethyl-, propyl-, isopropyl-, butyl-, and isobutylparaben

Sulfates, which are found in more than 70% of shampoos, face and body wash and hand soaps, are commonly used detergents that eliminate bacteria and give products that bubbly, squeaky clean effect. Highly effective cleansers, they are also potential irritants, with the ability to leave skin dry, brittle and in some cases, acne-ridden. While all sulfates were once wrongly linked to cancer, experts still have concerns over how certain sulfates are manufactured, through a process called ethoxylation, which contaminates the finished product with 1,4-dioxane, a known carcinogen. Commonly found ethoxylated sulfates include SLES and ammonium laureate sulfate.

PEGs, or polyethylene glycols, are a mixture of compounds and polymers that, when bonded together, allow for cosmetics to lubricate and penetrate the skin. You’ll often see the acronym followed by a number, which indicates the weight of that compound. In cosmetics, that number is lower, which allows for easier absorption. Not only can these PEGs help harmful ingredients get down deep into the skin, they also potentially contain 1,4 dioxanes and heavy metals like lead, iron, nickel, arsenic and more.

Phthalates are a group of chemicals often called plasticizers because they harden plastics found in hundreds of products, from automotive parts to raincoats to personal-care products like hair spray and nail polish. They, too, are endocrine disruptors, and contain reproductive risks with the ability to trigger signals in testicular cells that affect sperm function, says Leiba. You can avoid products that list phthalates in their formulation, but here’s an important footnote: The most commonly used phthalate is diethylphthalate (DEP), which is used as a solvent and fixative in fragrance. And the listing of individual fragrance ingredients in personal care products is not currently required by the FDA. This means consumers that see “fragrance” listed on the label can’t be certain whether phthalates are present or not—landing it high on the list of green chemistry’s next big issues to address, and one we’re watching closely. 

Formaldehyde Donors act as preservatives that help prevent bacteria from growing in water-based products, like nail polish, shampoo, and color cosmetics. Because brands don’t typically pour pure formaldehyde, a colorless, strong-smelling gas and known human allergen and carcinogen, into their products, many rely on these donor chemicals that, when added to water, decompose slowly and form molecules of formaldehyde. The slow release of these small doses of formaldehyde allow for a longer shelf-life, which in turn can actually increase the total amount released over time. 

Mineral Oil is a hydrocarbon often used as a dry skin emollient in niche beauty lines and drugstore staples alike. Because of its large molecular size and the fact that it’s processed, and made from petroleum (a known carcinogen), it remains on the surface, clogging pores, reflecting sunlight, acting as an allergen, and even increasing water loss when combined with paraffin, another hydrocarbon. Best instead to look for alternative oils, like flaxseed or sunflower seed oil, which is a vegetable oil containing naturally occurring conditioners like vitamin E.

BHA (butylated hydroxyanisole) and BHT (butylated hydroxytoluene) are synthetic antioxidants used as preservatives in lipsticks among other cosmetics—and they’re both loaded with concerns. Banned in Europe, BHA has been classified as a possible human carcinogen as well as an endocrine disruptor. BHT is a reproductive and developmental toxin, and has the ability to promote tumors in addition to mimicking hormones like estrogen. Both are also environmental toxins, with high potential for bioaccumulation in the world’s waterways, damaging wildlife and affecting the food chain.

Hydroquinone, an organic compound found in fragrance, hair conditioners, and, most commonly, skin lighteners, ranks in with a score of 9 as highly hazardous on the EWG Skin Deep database. That’s because the same mechanisms by which hydroquinone alters melanin in the skin also increase its exposure to UVA and UVB rays, meaning there’s a greater risk of skin cancer. It’s also associated with organ-system toxicity and respiratory tract irritation. Banned in Europe, Japan, and Australia, it is still permitted in personal care products in the U.S. in concentrations of up to two percent. Check labels for the ingredient but also for tocopheryl acetate, as hydroquinone is a possible impurity of synthetic vitamin E. 

Mercury and Mercury compounds may be naturally occurring substances by definition, but they are also toxic heavy metals, says Leiba, and can directly impact a woman’s menstrual cycle and ovulation, as well as cause kidney damage. The FDA banned the use of mercury as a preservative in cosmetics like skin creams at levels higher than 1 ppm in the 1970s (though that hasn’t stopped them from popping up on Amazon and eBay in recent years), but the chemical is still permitted for use in eyeliner and mascara formulations. Also an environmental toxin, mercury is often discharged into wastewater, entering the food chain as methylmercury. This is why certain kinds of fish are kept to a minimum in the diets of pregnant women, who are advised to stay away from high-mercury seafoods that can cause brain development issues in a growing fetus.

Retinol, the derivative of vitamin A, a nutrient that helps drive cell turnover, is proven to reverse signs of aging and act as an antioxidant—when used at night. When applied to sun-exposed skin during the day, however, “it can increase developmental lesions,” says Lieba, and increase the risk of skin cancer and irritation. Also worth noting: Retinol is now found in many chemical sunscreens, while conventional retinoids are often stabilized with BHT or parabens. For this reason, both of these retinol offshoots are banned from Westman Atelier formulas.