(The Hill) – An independent laboratory and healthcare research group found elevated levels of the cancer-causing chemical benzene in the majority of tested samples from several dry shampoo brands.

In a new study released Tuesday, Valisure said 70 percent of the samples it tested contained elevated levels of benzene, with some reaching up to 170 times the Food and Drug Administration limit of 2 parts per million (ppm).

Valisure tested 148 batches from 34 different brands, including from Not Your Mother’s, Sebastian and Batiste.

The healthcare and medical research group sent a petition to the FDA asking for a recall of the products it identified in the study and requesting updated guidelines for the regulation of benzene.

David Light, the CEO of Valisure, said “the detection of high levels of benzene in dry shampoos should be cause for significant concern since these products are likely used indoors, where benzene may linger and be inhaled for prolonged periods of time.”

“These and other issues identified by Valisure, including the detection of benzene in body spray, hand sanitizer, and sunscreen products, strongly underscore the importance of independent testing,” Light said in a statement.

Last month, Unilever, which makes beauty and personal care products, voluntarily recalled several dry shampoo brands, including Dove, Suave and Bed Head, because of elevated levels of benzene.

Benzene is a colorless or light yellow liquid that has a sweet odor. The chemical, which is both natural and manmade, evaporates into the air quickly and humans are typically exposed to it through inhalation.

According to the Centers for Disease Control and Prevention, benzene is one of the top 20 most commonly used chemicals in production.

Prolonged exposure to benzene is associated primarily with the loss of red blood cells and anemia as well as leukemia, cancer of the blood-forming organs.

In Valisure’s study, three batches from one brand contained benzene levels of more than 100 ppm, while 11 batches from three other brands contained more than 20 ppm. Even more products were found to have levels between 2 and 20 ppm.

According to Valisure, prolonged exposure to even just 1 ppm of benzene could result in the development of leukemia.

Light said one issue may be that raw, shipped materials and products are not rigorously checked, which can be risky due to companies using the global supply chain.

“Adding independent testing and certification into the supply chain could significantly improve the overall quality and help prevent these contamination issues from reaching consumers,” he suggested in a statement.