The head of the UN agency that provoked a massive outcry and some ridicule when it declared that bacon, red meat and glyphosate weedkiller caused cancer has defended its work, denying the announcements were mishandled and insisting on its independence.

Its outgoing director, Christopher Wild, fiercely defended the decisions and transparency of the International Agency for Research on Cancer (IARC), attacking the vested interests of its critics, many of whom are from multinational corporations.

Wild, a British scientist who has been at the helm for a decade, admitted in an interview with the Guardian that there might be a need to better explain to the public what it does in its monographs – the assessments it publishes of the scientific evidence on what, from mobile phones (possibly) to coffee (no evidence), causes cancer. He acknowledged the work was sometimes misunderstood.

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“The audience has changed. If you went back 10 to 15 years the audience for the monographs was a professional audience – regulatory agencies, scientists, policymakers of different kinds. Now there’s such an interest in cancer and its causes that there’s a general public audience,” he said.

Reaction to news that processed meat was carcinogenic spread around the world in 2015, with headlines such as “Save our bacon” and “Bacon lovers fry IARC”. But, said Wild, “I don’t think we mishandled it. I think it’s a question of roles. So our role is to synthesise the evidence. We look at whether something has the potential to cause cancer under some circumstances.”

He was slightly surprised at the furore. “The science was crystal clear,” he said. “We placed quite a bit of emphasis on the dose-response, if you like – the relationship between quantities eaten and effect.”

The IARC worked with the World Health Organization on a communications strategy. “Nevertheless we weren’t prepared for the scale of response and interest in that,” he said. “So it led to a lot of discussions in-house and with our colleagues in WHO on how we could better coordinate the scientific evaluation and then the advice on public health, which is their role.”

But there is a general misunderstanding of IARC’s classification system, he acknowledged. Tobacco, ultraviolet radiation and alcohol are all grade 1 carcinogens, which would surprise nobody, because they link respectively to lung, skin and liver cancers (and others). So is processed bacon and other processed meat. That does not mean that all are equally hazardous.

Grade 1 means the evidence is strong enough to be sure of the link to cancer. It is not an indication of how likely people consuming it are to get cancer. The IARC says 50g of processed meat a day raises the risk of colorectal cancer by 18%. That is still not high if you have a very low initial risk. Smoking, on the other hand, kills half of those who take it up.

On red and processed meat, Wild said, “a lot of the news outlets did say it’s about moderation and it’s not saying don’t eat red meat or don’t eat processed meat. But the part that was missing was something from us, together with WHO, in terms of a guideline on what this means for the public. That’s where we felt we needed to be working together much more closely in the planning process.”

The glyphosate monograph caused a different kind of storm. In January, Wild issued a rare statement attacking his critics. Since the evaluation in March 2015, it said, “the agency has been subject to unprecedented, coordinated efforts to undermine the evaluation, the programme and the organisation. These efforts have deliberately and repeatedly misrepresented the agency’s work. The attacks have largely originated from the agrochemical industry and associated media outlets.”

Major financial interests were in play, said the statement: the relicensing of glyphosate by the European commission, hundreds of lawsuits against Monsanto in the US over cancers allegedly caused by glyphosate and the decision by the Californian Environmental Protection Agency to label the herbicide as a carcinogen.

IARC classified glyphosate as grade 2a – probably carcinogenic in humans (on the basis of animal studies) – satisfying nobody. There are, said Wild, “huge vested interests on all sides. Obviously it’s a major commercial product particularly in relation to GM crops. At the same time there’s a very strong lobby against pesticides in general.”

The attacks included allegations about an adviser to IARC who, in the month that the monograph was published, signed a consultancy contract with two firms preparing to sue Monsanto.

What he has learned, said Wild, is the vital importance of public trust in the independence of scientists investigating controversial questions. “I think there’s not enough transparency,” he said. He has written a paper suggesting a “scientific passport – a voluntary code of declaration of their recent, let’s say, last five years’ consultancies and funding”.

IARC was set up in 1965 on a wave of postwar idealism with the idea that it would be part of a nuclear non-proliferation movement. It was proposed that France, the Soviet Union, the United Kingdom and the US would contribute 0.5% of their military budgets in a “fight for life”. That would have brought in $396m, most of it from the US, and was never likely. IARC started life with less than $1m. Now it has a budget of about $30m (£24m) annually, with speculation that the Trump administration may cut it back.

Wild’s association with IARC goes back to the mid-80s, but in 1996 he was appointed to a chair in molecular epidemiology at the University of Leeds and in December 2005 he became director of the Leeds Institute of Genetics, Health and Therapeutics. He became director of IARC in January 2009 and will leave having served two five-year terms.

In 2015, the agency celebrated half a century since its launch. Wild said there have been some big achievements. IARC has established the scale of cancer around the globe, helping countries to develop big data sets to know their own cancer burden and how well they are treating it. It has established the cause of some cancers that were a mystery, such as home-brewed alcohol fuelling oesophageal cancer in southern Africa and tracing kidney cancers in Romania to a Chinese herb that accidentally got into slimming pills. And it has evaluated prevention measures, establishing, for instance, that two shots of the jab against the HPV (human papilloma virus) against cervical cancer work as well as three, making it more practical and affordable to introduce in developing countries.