A report that found worrying levels of 27 pesticides in 1,400 towns across Brazil has caused alarm after news outlets published its online tool enabling readers to check their own water results. Eleven of the pesticides it found traces of are prohibited in Brazil and 21 of them banned in the European Union.

The report used data local authorities sent to Brazil’s health ministry between 2014 and 2017. While most test results fell within loose Brazilian safety limits, 12% of samples breached the EU’s stricter regulations, which researchers say shows Brazilian standards aredangerously lax.

“These are very toxic pesticides that cause a range of diseases,” said Marina Lacorte, a food and agriculture specialist at Greenpeace Brazil. “Brazilian society is consuming poison every day.”

The study was performed by the Swiss non-profit group Public Eye and investigative journalists from Repórter Brasil and Agência Publica. Tests performed twice a year by local authorities were released to investigators following a request under Brazil’s information access law. Brazil is an agricultural powerhouse and agribusiness makes up a quarter of its GDP.

Pesticides classified as “probably cancerous” by the US Environmental Protection Agency and that the EU believes cause endocrine dysfunction were among those that showed up in tests. More than half of Brazil’s 5,570 municipalities did not provide any test results at all, the report said.

Glyphosate – a popular herbicide classified as “probably carcinogenic” by the International Cancer Research Agency and subject of 9,000 lawsuits in the US – was found in 87% of tests. Atrazine, a herbicide listed as “highly hazardous” by the Pesticide Action Network and banned in the EU, was found in 84%.

The EU has established a uniformly low limit applicable to all pesticides, said Public Eye researcher Laurent Gaberell, whereas Brazil sets different limits for each substance. Unlike Brazil, the EU also legislates against mixtures of pesticides, which can be more dangerous when combined.

“Brazilian limits do not take into account this cocktail effect,” Gaberell said. “In the EU we have a very strict regulation for pesticide residues in water but we allow European companies to pollute the drinking water of other countries at levels that would be illegal here.”The Brazilian government, water companies and pesticide developers have moved to try to reassure customers.

The São Paulo water company Sabesp said in an email that its water was safe and tested daily. The National Association of Plant Defence – a pesticide developers’ association – called the report “alarmist”. “The text imports European parameters and performs an analysis beyond the context of Brazil, a tropical country with more than 65% of its territory covered by native vegetation,” it said.

Brazil’s health ministry said it was carrying out a nationwide study into pesticides in water and that it was too soon to draw conclusions. “Exposure to pesticides is a public health problem and each situation should be analysed differently,” it said in a statement.

Cassiana Montagner, a chemistry professor and environmental chemistry researcher at the University of Campinas, questioned the report’s numbers showing increases in the quantity of pesticides from 2014 to 2017 because it did not take changes in testing techniques into account.

But she also called it a “positive alarm”. “Brazil uses a lot of pesticides and there should be a discussion on whether this is necessary,” she said.

This year alone, the new government of far-right president, Jair Bolsonaro, closely allied to the agribusiness that makes up a quarter of Brazil’s GDP, has approved scores of new pesticide products. A controversial bill to lift restrictions on pesticides is stuck in Congress.

“While EU is prohibiting more here we are freeing up more. We are heading in the opposite direction,” said Lacorte.