The World Health Organization says it has seen no evidence to support a German backlash against tough EU air pollution limits.

The country’s transport minister, Andreas Scheuer, sent a letter to the European commission last week calling for a review of the EU’s nitrogen dioxide (NO 2 ) limits, despite signs of a government split over the issue.

Scheuer’s claim that “increasing voices” in Germany’s medical profession were casting doubt on the science behind clean air benchmarks provoked a strong response from the EU environment commissioner, Karmenu Vella, who said if the limits were changed they would only be made stronger.

The dispute followed an open letter by 107 German lung specialists who argued that health fears about vehicle exhaust emissions had been overblown.

Prof Dieter Köhler, the paper’s author – and a former president of Germany’s Federal Association of Pulmonologists, Sleep and Respiratory Doctors (BdP) – is in Brussels for talks with senior EU environment over the issue, even though the BdP has disowned his opinion, describing the initiative as ill-informed “populism”.

The WHO’s climate and health team leader, Diarmid Campbell-Lendrum, told the Guardian the German material published so far should not be considered as a basis for discussion.

“We need evidence to be published in a peer-reviewed journal and properly reviewed by experts,” he said. “We have heard the discussion but we’ve seen nothing that constitutes evidence, from our point of view. And we have guidelines that are based on thousands of scientific papers and drawn up by the world’s best possible experts.”

Germany’s transport minister, Andreas Scheuer, has asked the European commission to review the EU’s nitrogen dioxide limits. Photograph: Lukas Barth-Tuttas/EPA

Germany is one of several countries, including the UK, facing European court action for violating the air-quality directive, and its car industry has been scarred by Dieselgate, the Volkswagen emissions scandal.

The EU’s environment wing views the underlying science of Scheuer’s claims as suspect. Officials believe the medics’ open letter contains no new data and say its signatories represent only 3% of the BdP’s 4,000 members.

One EU source stressed that Tuesday’s meeting would not be allowed to influence a nearly completed fitness check of the EU’s air-quality directive, and had only been arranged as a “courtesy” to the doctor.

“If his visit is merely a coincidence, it’s a remarkable one,” the source said, noting the German government’s recent loss of 16 domestic air pollution court cases. “There was no debate on NO 2 prior to that.” The initiative had received “strong party political support” in the European parliament, the source added.

Köhler will be appearing at meetings in Brussels with German conservative MEPs, including Peter Liese, a right-leaning member of the European parliament’s environment committee.

Liese said he had wanted to help Köhler, whom he had known for years. “I don’t say he is right but he has important points to make and and I want responsible people in Brussels to listen,” he said. “When we want to maintain support for EU environmental policy, we need to react to legitimate criticism.”