The Poison Pipeline

Brazil, an agricultural superpower, is one of the world’s biggest consumers of pesticides. In 2020, it banned paraquat after its health regulator found strong evidence that occupational exposure to the chemical causes Parkinson’s disease. But the ban hasn’t stopped paraquat from entering the country.

An investigation by Lighthouse Reports, Bloomberg and Repórter Brasil found paraquat in the country’s drinking water, along with carbofuran and aldicarb, two other pesticides banned in Brazil.

Our analysis found that a third of Brazilian municipalities that tested their water between 2023 and 2026 detected banned pesticides, and 28% found traces of paraquat. In the agricultural state of São Paulo, almost 60% of tests detected at least one of five banned pesticides.

Because paraquat disappears from water within months, experts say the test results indicate that it’s still being used regularly.

We examined the illicit global trade and uncovered a supply chain that stretches from manufacturers and exporters in China, through transit countries such as Paraguay, to smugglers who bring paraquat and other banned chemicals into Brazil.

Over the past decade, China has labelled hundreds of pesticides as “export-only”, banning them at home while shipping them around the world. Its list includes paraquat, aldicarb and carbofuran.

“People no longer trust what’s coming out of their tap,” said Cassiana Montagner, coordinator of the environmental chemistry lab at the University of Campinas, outside of São Paulo. “That’s why you see more bottled water, more filters at home. But a lot of people can’t do that. A lot of people still need to use this water.”

Karen Friederich, a toxicologist at Brazil’s Institute of Science and Technology in Health (Fiocruz), said something similar, “The contaminated water isn’t only a danger to those who drink it. It also sits at the start of the production chain, carrying this contamination into other water systems and rivers. The impact reaches beyond farmworkers, affecting everyone who lives in these communities.”

The problem isn’t limited to Brazil. Paraquat is still used in the US, and around the world, governments are failing to carry out credible monitoring of how pesticides affect human health.

METHODS

Reporters analyzed Brazilian water tests and global trade data to trace the presence of banned pesticides, such as paraquat, through the supply chain.
Under Brazil’s Drinking Water Quality Surveillance Information System, or SISAGUA, water is tested in municipal drinking water systems and private wells near farms, factories and other businesses. Brazil requires testing for pesticides twice a year, but not every municipality complies.

The tests cover 40 active ingredients, including five chemicals that are banned in Brazil: aldicarb, carbendazim, carbofuran, methamidophos and paraquat. Hundreds of other registered active ingredients aren’t covered. Bloomberg examined tests from January 2023 through June 2026. Before then, testing for certain banned pesticides was not required. Legacy persistent pesticides listed under the Stockholm Convention, including DDT, were excluded from the analysis.

Agricultural states, identified by gross value of agricultural production (Valor Bruto da Produção Agropecuária) from 2023 to 2025, were more likely to have banned pesticides detected in water.

The Ministry of Health identifies chemicals in water samples when found above the limit of detection or above the limit of quantification. For each chemical, we counted a detection if a test included a quantification value or if at least two trace-level samples (detected, but not quantifiable) from the same municipality came from labs that passed data quality checks.

Just under half of the nearly 9,000 lab branches marked every tested banned chemical as detected in trace amounts. We treated the blanket trace results as data-entry errors and did not count those detections.

We also discarded samples when the concentration matched the limits of detection or quantification. Researchers familiar with SISAGUA warned that these values may be placeholders used by labs rather than actual measurements.

In some cases, the limits of quantification and detection were empty even though results showed concentrations of banned chemicals. In those cases, if the analytical limits were reported properly in more than three-fourths of the lab’s other samples, we included the results. If not, we checked the distribution of that lab’s concentration readings. If recurring values accounted for 70% or more of them, we didn’t count the samples as detections. Two chemists reviewed our approach, which yielded detection rates below the Ministry of Health’s results.

We also tried a more stringent method that counted only quantifications as detections. Experts said this would undercount tests detecting banned pesticides. Even under that method, the analysis found tests regularly detected banned pesticides.

We also analyzed paraquat imports from January 2025 to September 2026 using Big Trade Data, a commercial database of international trade and customs declarations.

Big Trade Data provides gross shipping weight. Absent reported concentrations, we estimated paraquat weight based on product type under the Harmonized Commodity Description and Coding System, or HS, for formulated products (HS 3808.93), at roughly 20% paraquat by weight, and “pure” technical grade (HS 2933.39) at 40%. These are lower-bound estimates.

Trade records include origin and destination countries as well as the exporter name. Because HS codes cover broad categories of chemical and herbicide products, we narrowed the data to paraquat shipments by searching product descriptions for the chemical name, trade names such as Gramoxone, and Chemical Abstract Services registry numbers.

About one-fourth of the paraquat volume we analyzed — and nearly one-third of individual shipments — lacks an exporter name. For those records, we inferred origin from the port of departure. To identify potential smuggling hubs, we compared paraquat imports with cropland, using the total hectares of temporary and permanent crops in 2023 from the World Bank.

Big Trade Data does not directly capture exports reported by mainland China or Hong Kong, so we used customs data from more than 70 importing countries.
To check for gaps in Big Trade Data, we cross-referenced it with United Nations Comtrade and Trade Data Monitor for imports of chemical compounds with a “pyridine ring” (HS code 2933.39), the umbrella trade code that includes paraquat and diquat. We found comparable volumes of imports within 10% of the other three sources for Brazil, Paraguay, and Uruguay in 2025. Coverage was lower for the United States, and higher for Indonesia and Ghana (roughly 9 times higher).

STORYLINES

Terezinha Junglos, whose first name means “little Teresa” in Portuguese, has worked as a farmer since she was seven years old, growing tobacco in Santa Catarina, a state in southern Brazil. She never imagined her work would leave her seriously ill.

In the tobacco fields, she grew used to the spraying of pesticides, a practice locals call batendo o veneno, which translates to “hitting the poison”.

Terezinha spent years handling pesticides, often ending up with her clothes soaked in them. No one ever taught her how to handle them safely.
She sometimes used Gramoxone, a herbicide made with Paraquat commercialised by Syngenta, to kill the weeds. She also used Furadan, an insecticide made with Carbofuran.
At 30, she began to tremble, developed chest pains and lost her appetite. Within a year, she became the second person in her family to be diagnosed with Parkinson’s disease. Her aunt, also a tobacco farmer, would later be diagnosed too.

Terezinha is not alone. Across Brazil, doctors are diagnosing Parkinson’s disease in young patients, predominantly farmworkers, who report being exposed to paraquat.

Míriam Carvalho, a neurologist in northeastern Brazil, said she routinely asks about pesticide exposure when a very young patient is diagnosed with Parkinson’s disease. Through Brazil’s public health system, she sees mostly farmworkers and poor rural residents. “It really catches your attention,” said Carvalho, who has several patients in their 30s and 40s, almost always with a history of long-term exposure. “It’s not at all uncommon for us to come
across this profile.”

Syngenta in June discontinued paraquat sales globally and halted the chemical’s production at a UK facility. But the company is a subsidiary of a Chinese state-owned conglomerate, Sinochem Holdings, one of at least a dozen companies in China that export paraquat to the US. Sinochem did not respond to a request for comment.

A spokesperson for FMC Corp. did not address why it halted production of carbofuran in 2019 but said the company shares “the serious concerns about the dangers of illegal and counterfeit pesticides.” In an emailed response, a Syngenta representative said the firm’s decision to stop paraquat production in the UK was “made solely for commercial reasons.”

The Chinese embassy in Brazil didn’t respond to a request for comment on this article.

CO-PUBLICATIONS

• Bloomberg: The Poison Pipeline
• Repórter Brasil : Forbidden pesticides appear in one in seven municipalities in Brasil