Cosmetics, including eyeliner, commonly contain toxic heavy metals, which are all known to be harmful or even cancer-causing, according to EmaxHealth. Though these metals are not added to the products deliberately, being primarily by-products of the manufacturing process or contaminants of raw materials, companies do not reveal their presence on labels. As of June 2014, consumers have no way of knowing what chemicals are in their cosmetics.
A 2011 study published by Environmental Defense of Ontario, Canada, found seven out of eight toxic heavy metals in all 49 products tested, including four concealers, five foundations, four powders, five blushes or bronzers, seven mascaras, two eyeliners, 14 eye shadows, and eight lipsticks or glosses, according to EmaxHealth. The heavy metals tested were arsenic, cadmium, lead, mercury, beryllium, nickel, selenium, and thallium; only mercury was not found in any of the products. Although Canada bans all of these products from cosmetics, the United States does not. These dangerous metals accumulate in the body over time, as they are absorbed through the skin, and are associated with health problems ranging from headaches, nausea and vomiting to cancer, neurological problems, memory loss and reproductive problems.
Toxic metals are not the only chemicals of concern in cosmetics, according to Organic Authority. Formaldehyde, which is a carcinogen, is commonly used as a preservative in cosmetics. Parabens, chemicals which are known carcinogens and hormone disruptors, also appear as preservatives in many cosmetics. Phthalates, which are known endocrine disruptors, appear listed as "fragrance" in many cosmetics and personal care products.
Safer products are available. Organic Authority recommends the Environmental Working Group's "Skin Deep" list of tested beauty products. The list ranks safety of various products including eyeliner, mascara, foundation, blush, nail polish and other personal care products.