Sauvignon Blanc grapes are dropped into a bin during harvest in St. Helena, Calif. The Department of Pesticide Regulation issued temporary guidelines on May 9 for chlorpyrifos while it considers long-term regulations. (Eric Risberg/AP)
Shana Bernstein is a historian and clinical associate professor of legal studies and American studies at Northwestern University, and is the author of "Bridges of Reform: Interracial Civil Rights Activism in Twentieth-Century Los Angeles."

A few weeks ago, California joined New York and Hawaii in banning chlorpyrifos, an agricultural pesticide that has been blamed for brain and neurological development issues in children living and attending school near the fields where it’s used. This came on top of jury verdicts in favor of plaintiffs who sued Monsanto, claiming that its popular pesticide Roundup had contributed to their developing cancer.

These events signal that the tide may be turning in a half-century battle against toxic pesticides. Activists have used a variety of strategies to target the dangerous effects of pesticides at the state and federal levels. But they have mostly been successful only at the federal level by focusing on individual pesticides with a proven track record of harm. This has allowed other dangerous pesticides to pass muster with the Food and Drug Administration and the Environmental Protection Agency because regulators have focused more on corporate well-being than on protecting public health.

Fifty years ago this summer, the Senate Subcommittee on Migratory Labor held hearings on pesticides after the United Farm Workers (UFW) managed to get the attention of the committee chaired by Sen. Walter Mondale (D-Minn.).

Congress was paying attention partly because of a boycott that had won over American consumers. As part of its campaign to protect its members from exposure to toxic chemicals such as DDT and Aldrin, the UFW began a consumer boycott of grapes. This was a smart move because while grape buyers might not be moved to act to protect the workers harvesting grapes, they were alarmed to learn that pesticides, specifically the residue left on produce, made the fruit unsafe to eat. This enlisted consumers into the UFW’s fight to protect farmworkers, whose bodies were on the front lines of pesticide exposure.

The hearings helped the UFW prove the public could not trust the Food and Drug Administration’s claims that widely used agricultural pesticides were safe, for consumers and workers. They also showed a weakness in state-level regulations. A UFW study revealed that residues of DDT, a suspected human carcinogen, were on California grapes sold in Washington state grocery stores, despite claims to the contrary from state regulators.

The UFW also revealed that grapes sold at a California Safeway store were contaminated with the toxic pesticide Aldrin, linked to convulsions and kidney damage among other human health effects. Growers had claimed that Aldrin hadn’t been used in three years, but Safeway’s independent tests confirmed its presence. Instead of investigating how the pesticide found its way onto the grapes, the FDA and growers simply questioned the tests’ accuracy without even checking the reports.

The emphasis on consumer safety worked. A few months later, California’s state agriculture regulators barred 91 pesticides from use on crops and planned to impose restrictions on 120 others. Many growers were forced to sign UFW contracts banning chemicals such as Aldrin and DDT. Contracts also specified that growers monitor farmworkers’ pesticide exposure using the same standards California state law already required for crop dusters and pesticide industry workers.

UFW activism also helped propel federal policy shifts by connecting consumer and farmworker interests to environmental issues that concerned the newly created Environmental Protection Agency. The combined efforts of the UFW, environmental groups and other organizations resulted in federal bans of many toxic pesticides, most prominently DDT, which endangered the environment, including birds and aquatic life, and had potentially dangerous effects for people. Emphasizing the combined dangers pesticides posed to consumers, workers and the environment was effective.

And yet, despite these advancements, U.S. regulatory agencies continued to favor business and profits over public health and environmental concerns, especially if there was any uncertainty about pesticides’ dangers.

For example, 50 years later, products like Roundup are still on the market. Many homeowners and gardeners use it to control weeds but are unaware that, while some studies find no definitive cause for concern, others, including one from the World Health Organization’s International Agency for Research on Cancer, have deemed glyphosate, the herbicide used in Roundup, “probably carcinogenic to humans.” Besides possibly putting workers and property residents at risk, glyphosate is implicated in undermining bees’ health, and many scientists suspect that it may negatively affect the environment over time as well.

Why the discrepancy between the swift ban on DDT and the delay on Roundup and other pesticides, which remain on the market despite seeming to threaten public health and the environment? Because at least some of DDT’s dangerous consequences were fairly immediately apparent, including how it decimated the bald eagle population. By contrast, for pesticides that may cause cancer (including DDT), the health consequences may not appear for decades after exposure. This produces uncertainty, making it easier for pesticide companies to fend off stricter limits and stronger oversight. The result is that agencies such as the EPA, Health Canada and the European Food Safety Authority have concluded that glyphosate is safe — although eight out of 15 of the EPA’s scientists disagreed.

But there’s hope. Like the campaign that the UFW waged 50 years ago, regulatory successes are happening at the state level. And this time, the efforts are being furthered by judges and juries as well.

Plaintiffs are suing Monsanto over Roundup — and winning.

In August, a state court in San Francisco ordered Monsanto to pay $289 million to groundskeeper Dewayne Johnson, 46, after a jury concluded that workplace use of Roundup contributed to his non-Hodgkin’s lymphoma. His legal team presented internal Monsanto emails that, they argued, showed Monsanto knew and ignored evidence that Roundup wasn’t safe.

In March, a federal jury ordered Monsanto to pay $80 million to Edwin Hardeman, another California man who claimed that using Roundup to control poison oak and weeds on his property was a substantial reason he now has non-Hodgkin’s lymphoma. And just last month, jurors in a third case awarded more than $2 billion to a couple in Livermore, Calif., who argued that using Roundup to control weeds since it was introduced in the 1970s contributed to their non-Hodgkin’s lymphoma as well. An additional 11,000 lawsuits are pending in the United States. (Monsanto did not respond to a request for comment.)

Just like states got out ahead of the federal government half a century ago in limiting the use of dangerous pesticides, they are once again erring on the side of caution to protect public health, as evidenced by California, New York and Hawaii’s actions against chlorpyrifos.

The problem is that action on a state-by-state and pesticide-by-pesticide basis is insufficient. We need to rethink and reorient our entire system of pesticide regulation to focus on public health and environmental concerns and to consider the less certain long-term consequences alongside the immediately clear ones. Consumers, environmentalists and workers all must recognize their common cause and urge their state legislators and national lawmakers to pass measures insisting that regulatory agencies err on the side of caution regarding all such chemicals. And then regulatory agencies must provide the oversight to make sure it happens.

Why? Because focusing on one pesticide at a time, and only those that pose clear and immediate risks, is how we got here. Even though the United States banned DDT in 1972, chemical companies merely introduced other toxic pesticides. Our regulatory system must favor caution, putting public health before corporate profit. The risk of not doing so is far too great.

[CORRECTION: An earlier version of this story did not highlight the uncertainty about the link between ingested glyphosate and cancer.]