Plastic not so fantastic

Questions about the safety of some plastic bottles are finding few answers in this country, Chris Barton, of the NZ Herald, reports.

Prof Ian Shaw doesn't use cling film to wrap his sandwiches.

He prefers greaseproof paper.

He also won't microwave food in plastic containers.

And he would never, ever, feed a baby with a plastic bottle made with a chemical called bisphenol-A.

"I tend not to use plastics for packaging," says the University of Canterbury professor of toxicology.

So there was some amusement when one of his PhD students brought him an unexpected Christmas present.

"A student came with an article saying there was environmental estrogen in some greaseproof papers.

"It made his day."

Prof Shaw's specialty is the mechanisms and impact of environmental chemicals on human health - in particular those that mimic hormones, such as the female hormone estrogen, known as endocrine disrupters.

With something like 80,000 synthetic chemicals around us and 1000 new chemicals created every year, endocrine disrupters are everywhere and often turn up where you least expect them.

So Prof Shaw isn't surprised that there may be some in his wrapped lunch.

But he is concerned that regulatory authorities aren't taking the wider issue seriously.

"What we need to do is decrease the residues of these compounds in our diet.

"It's crucially important we do that."

It's a view that gets him offside with the New Zealand Food Safety Authority (NZFSA), especially in relation to one of the most ubiquitous endocrine disrupters in the environment - bisphenol-A or BPA.

It's widely used in the manufacture of polycarbonate plastic drink bottles and packaging, and in the lacquer that lines food and drink cans.

BPA leaches, in small amounts, into the food and drink contained by these linings and plastics.

The end result is that tiny amounts of BPA end up in us.

Tests have consistently found the chemical in blood, urine, umbilical cord blood and in the amniotic fluid protecting a fetus.

The NZFSA says BPA is safe as long as no-one exceeds the "tolerable daily intake" level of 0.05mg per kilogram of bodyweight per day.

Prof Shaw, who is a member of NZFSA's Food Safety Academy, disagrees.

He believes there are good reasons to be limiting exposure to BPA even at low levels.

"I'm not the sort of person who likes to ban everything, but I am the sort of person who likes to minimise exposure to compounds that might have a risk.

I think the evidence is overwhelming that these compounds are having an effect on humans even if we can't prove it absolutely."

He is not alone:

• Last month the head of the United States federal agency studying BPA safety said pregnant women, infants and children should avoid ingesting the chemical.

• Last September Breast Cancer UK launched a "No More BPA" campaign citing studies that showed pre-birth and early exposures could lead to changes which predispose the body to develop breast cancer later in life.

• In July a group of French senators tabled a Bill calling for a ban on the use of BPA in food contact materials.

• In October 2008 the Canadian Government announced it would prohibit the importation or sale of bisphenol-A in bottles and food packaging for infants and newborns.

The problem with chemicals like BPA is that they are great pretenders - similar in their molecular structure to hormones, particularly the female hormone estrogen.

So good is their disguise, they can fool the body into believing it is reacting to a natural hormone.

The sort of health problems that can result from such an interaction include reduced sperm count, early puberty in girls and increased incidence of breast and testicular cancer.

Importantly, the chemicals don't necessarily need to be at high levels to have an effect.

The NZFSA points out on its website that "some studies in laboratory animals suggest that low levels of [consumed] BPA may have an effect on the reproductive system".

But it then goes on to say "similar consequences in consumers at these low concentrations are considered unlikely because BPA is rapidly inactivated and then excreted in the urine".

Prof Shaw says that's a naive argument.

"It's naive because the fact that it's in urine means we've been exposed to it.

"It's gone through us and it might have had its effect en route."

It also doesn't mean that the chemical has been entirely expelled from the body.

"It's a steady state situation we are constantly exposed to every day and we're constantly excreting "every day which means we have a constant level in our blood.

"In other words there is an additive effect.

"If you have infinitesimally tiny concentrations but an awful lot of infinitesimal concentrations they add up to a much higher concentration that could have a real impact."

Prof Shaw and his researchers have looked at the level of estrogenic compounds in an everyday New Zealand diet and found when the hundreds of different types - both natural and artificial - are added up there is a circulating level of estrogenic chemicals that is likely to have pharmacological effect.

Two chemicals - BPA and genistein - stand out at relatively high levels.

Genistein is a naturally occurring estrogen receptor found in a number of plants including fava (broad) beans and soybeans.

The array of estrogenic compounds is what makes proving cause and effect so difficult, plus the fact that the effect often occurs several years or even decades after the exposure.

Which is why the research to date remains inconclusive.

Trying to show, for example, that precocious puberty is related to exposure to a particular environmental estrogen is an almost impossible research task because there are so many variables.

On the other hand, it's well documented that the human sperm count in New Zealand is in decline and it's not hard to reach the conclusion that endocrine-disrupting chemicals are to blame.

"It's scientific hearsay in a way," says Prof Shaw.

"We know we're getting much more exposure to these chemicals and we know we're getting a greater incidence of these weird effects on sexual development.

"It seems they are connected."

Prof Shaw says a key area of research is whether chemicals like BPA and genistein cross the placenta and, if they do, what the impact is on the developing fetus.

"The hypothesis is that if you get exposed during that key decision-making period in foetal development it could be crucially important - it could decide whether the fetus develops male or female characteristics."

John Reeve of the NZFSA is unconvinced by Prof Shaw's case.

"Personally I didn't agree with him in terms of the toxicology.

"You can theorise there might be a problem but we haven't got any data yet."

Reeve argues that BPA is not a particularly good endocrine disrupter.

"This is where a lot of the problem is in this whole area of endocrine disrupters.

"You can actually show chemicals do have an effect there, but often the effect is extremely low compared to the level of estrogens that are actually floating around in the body already."

As Reeve sees it, the question is whether the effect is enough to cause a change in the physiology of an animal.

"That's where we would go back and look at the animal studies and they just don't throw up any evidence which would suggest you have a problem."

But animal studies showing adverse effects from BPA were enough to convince Canadian regulators that high-risk groups such as babies ought to be protected.

Last year Reeve also told the Food Safety Academy - the NZFSA's independent experts - that a panel assembled by the United States' National Toxicology Programme had reviewed all available data on BPA and concluded that "for some developmental outcomes for exposed infants and fetuses, there is some concern as to the safety of the levels of BPA leaching out of plastics and can linings into infant foods".

The NZFSA is also awaiting data commissioned by the United States Food and Drug Administration to resolve issues that have been raised regarding previous assessments on the safety of BPA.

Prof Shaw, who admits he has the biased viewpoint of "someone who is interested in the biochemical effects of these compounds in people", says the way forward is to ask the question whether we really need these compounds to pack our foods in.

He says it's important to be careful because food packaging is crucially important to the decrease in food-borne illness.

"I would want a question to the industry to say, 'Can you replace this packaging with something else?'."

He'd suggest a phase-out of the old for viable alternatives over something like a five-year period - assuming of course the new packaging is thoroughly tested to make sure it isn't something worse.

Prof Shaw says if the goal is to decrease the risk of exposure to estrogenic compounds, decreasing BPA in food packaging would help achieve that, because it reduces our overall exposure.

On the other hand, there are other chemicals that are naturally in food, such as genistein.

"Should we be saying to people you shouldn't eat soy?", Prof Shaw asks.

"Of course you shouldn't.

"But what we might be saying is, 'Should we really be using quite as much soy as we currently are in foods?'."

The example Prof Shaw uses is bread in New Zealand, which almost always includes soy.

So is NZFSA having such a dialogue about replacing BPA with our plastics industry?

"As there is currently no evidence of a food safety issue there is no need for NZFSA to discuss BPA with manufacturers.

"Any decision to use alternative materials is purely commercial," says Reeve.

In part, it is already happening.

Consumer NZ noted on its website in March that the six largest manufacturers of baby bottles in the United States said they would stop selling products made with BPA.

"This was after politicians asked them to voluntarily stop using the chemical - a decision made easier by major retailers no longer selling these bottles."

Consumer NZ says it expects such decisions to have a flow-on effect here.

To some extent that is happening with BPA-free baby bottles and sports drinks bottles available to savvy shoppers.

As for getting advice about the issues involved, it isn't straightforward.

Plunket, for example, carries no information about BPA-free bottles on its website.

When mothers ask, it refers them to NZFSA.