When you read the label of a chemical cleaner, pesticide or other product, you may have noticed that those labels contain information about any potentially harmful ingredients and the percentage of each. Often, those labels are required by a federal law called the Federal Insecticide, Fungicide and Rodenticide Act and enforced by the Environmental Protection Agency.

Manufacturers aren’t required to list every single ingredient, however, because doing so might give away trade secrets. To protect public health, however, any ingredients not listed must be inert — benign substances that pose no risk — and the total percentage of those inert ingredients must also be listed. The EPA is tasked with determining what ingredients are inert, and which ones require specific disclosure “to protect against unreasonable risk” to humans and our environment.

According to a lawsuit just filed in federal court in San Francisco, however, many of those “inert” substances aren’t benign at all. Three groups — Physicians for Social Responsibility, the Center for Environmental Health, and Beyond Pesticides — claim that many pesticide ingredients get rolled up into that “inert” category despite being just as dangerous as those for which the law requires specific disclosure.

Currently, the EPA essentially considers a chemical inert if it doesn’t react to other chemicals when mixed with them. That reactivity standard, according to the plaintiffs, simply doesn’t cut the mustard.

Over 370 commonly used chemicals have been identified as inert by pesticide manufacturers and the EPA, the plaintiffs say, that have been shown to be hazardous. Several are known or suspected to cause cancer, neurological disorders or reproductive harm. Ninety-six of the “inert” chemicals are on the EPA’s own “high priority for testing” list.

Depending on the exact chemical mixture, some of the so-called inert ingredients may become active — and be just as toxic as many other active ingredients. Others may not pose a risk on their own, but can cause the active ingredients to be inhaled or absorbed more easily, make them harder to wash away, or reduce the protection offered by rubber gloves or other protective equipment.

Moreover, the groups claim the EPA has long had this information but has failed or refused to take action. In 2009, it seemed the EPA was reconsidering the issue. Unfortunately, the agency dropped the ball, according to the plaintiffs — leaving us all with a false sense of security about our chemical safety.