How safe is that salad?

The potential danger of agricultural chemicals in food can be an emotive issue. Chemicals such as pesticides, herbicides and fungicides are widely used and to a degree make low-cost, large-scale industrialised farming possible. Many of these substances are known to be dangerous to human health and the environment at high doses, and in New Zealand rigorous testing and sound research keeps their presence within safe levels. Yet some people believe we should be avoiding agrichemicals in food altogether.

Certainly, there’s no question whether these substances are present in our food.

Research conducted by New Zealand Food Safety Authority (which has since become part of the Ministry for Primary Industries, or MPI) in 2010 found that 94 per cent of the fruit and vegetables sampled (both from New Zealand and overseas) contained traces of agricultural chemicals. Nearly half of the imported cucumber samples tested, for example, contained endosulfan – a chemical which is banned from use in New Zealand and 62 other countries.

Earlier research by the NZSFA also found fruit and vegetables can contain a cocktail of substances; some celery for instance was found to have traces of up to 21 different chemicals.

However, the majority of the samples tested found agrichemicals within acceptable levels – and the MPI says that even when tests found growers had exceeded maximum levels, the food was still safe to eat because the maximum residue limits are set so conservatively.

So how does the MPI come up with these guidelines? And do they really reflect levels of chemicals in food that are safe?

Testing for safety

The MPI is responsible for ensuring the safety of the food we consume. Its Science and Risk Assessment arm conducts a five-yearly Total Diet Survey which assesses the levels of chemical residues in food. They also conduct annual tests on a range of difference produce.

The official guidelines for safe levels of agrichemicals in food have been established internationally over many years by organisations such as Codex Alimentarius Commission (an international body responsible for food standards worldwide), the World Health Organisation and OECD chemicals programmes. The MPI follows these guidelines. Produce testing takes place in laboratories on behalf of the ministry with both New Zealand-grown produce and food from overseas tested.

Ministry of Primary Industries (MPI) director for systems and support Debbie Morris says there are robust systems in place for checking levels of agrichemicals in food.

“As part of New Zealand’s regulatory system MPI has extensive monitoring programmes in place, which look at agricultural chemicals, contaminants and microorganisms in our food.”

She says that the most recent Total Diet Survey results showed little cause for alarm.

“A total of 123 different foods were tested. For all the eight age-sex groups considered, the dietary exposures to the 241 agricultural compound resides tested for were all well below acceptable daily intake (ADI) levels.”

It’s also important to note that there is a very large body of evidence supporting the health benefits of eating lots of vegetables and some fruit every day.

“Most of us don’t eat enough vegetables and fruit,” says nutritionist Rose Carr. “So it would be disappointing if the detectable presence of pesticide residues put anyone off eating more; especially those all-important vegetables. There is simply no evidence that we are doing any harm by consuming foods that fall well within the current safety standards.”

Critics of the tests

Alison White is spokesperson for the Safe Food Campaign, a group set up to highlight the dangers of agrichemicals in New Zealand food. Alison, who has a masters degree in public health, says the testing commissioned by the MPI is not foolproof.

She believes the maximum residue limits that are used as a guide for safe levels of agrichemicals in produce don’t take into account the effects of the kinds of chemicals that cause endocrine disruption or immune system suppression.

“There is a substantial body of evidence to suggest that there is no safe level of a substance which can cause endocrine disruption and immune system suppression,” she says.

Also, pesticide detection methods always have a threshold below which residues cannot be detected, even if they are actually present, Alison says.

“When no pesticide residue is detected, calculations on safety are made assuming that there are no residues at all, even if there are.”

Alison believes there are other limitations in the testing commissioned by the MPI. For instance only eight samples of a particular fruit or vegetable are tested, she claims: “Can we assume that kiwifruit, for example, is safe to eat in New Zealand based on the results of eight samples?”

The bad guys

Clearly there are traces of agrichemicals in much of the food we consume. Any debate, then, is about how much – if any – is okay.

At first glance it might seem crazy to allow any chemical in our food that might be harmful, yet we often allow dangerous chemicals into our diet when we see benefits. Both salt and alcohol, for instance, have proven links to serious health issues – and many New Zealanders have a risk-management approach to their use.

Of course, two wrongs don’t make a right, and we should be aware that there are also proven dangers to high-level exposure to some of the agrichemicals that are permitted in our food. Some of the studies that link these chemicals to disease deal with exposures many, many times New Zealand’s permitted levels, which doesn’t prove that lower levels are therefore dangerous. However it’s worth being aware of the results, especially as many of these chemicals can affect the broader environment.

One study from 2006, for example, dealt with chlorpyrifos, an organophosphate insecticide which has been used here for over 20 years. The research, published in the journal Pediatrics, evaluated the cognitive and motor development of children who had been exposed to the chemical

in New York City, where it had been used to kill pests in apartments. The children exposed to chlorpyrifos were found to have significantly slower mental and motor development at the age of 3 than those who hadn’t been.¹ The chemical has also been shown to be highly toxic to fish, bees, and amphibians.²

Another study, from 2011, linked chlorpyrifos to Gulf War Syndrome, an illness that affected about a quarter of the veterans of the 2001 Gulf War. The chemical was used to keep bugs at bay in soldier’s quarters.³

Another chemical found in New Zealand food is chlorothalonil, a broad spectrum fungicide. It is classified as a “probable human carcinogen” by the US’ Environmental Protection agency (EPA)⁴, and is also dangerous to the environment. A 2012 study by the University of South Florida revealed that the chemical was lethal to a wide array of freshwater organisms, and that it killed snails, algae and aquatic plants at doses below those deemed safe by the EPA.⁵

And Mancozeb, also registered for use in New Zealand, is a fungicide that breaks down to produce ethylene thiourea, which is classified as a probable human carcinogen by the EPA.

Even the familiar Roundup has come under scrutiny. The University of Pittsburgh revealed that Roundup use near rivers, streams and lakes caused a 70 per cent decline in amphibian biodiversity.⁶

The cocktail effect

The adverse effects of single agrichemicals have been well researched, but the effect of ‘chemical cocktails’ – where multiple substances interact – is harder to quantify.

Meriel Watts of the Pesticide Action Network believes that food testing by NZFSA doesn’t take into account this effect.

“Pesticides can have additive effects, so that in essence the toxicity of the residues of two pesticides may be double that of each one by itself, and that is how the safe level is assessed – each pesticide is looked at as if it is the only one present.

“There may also be synergistic effects between residues, where the toxicity of two pesticides together is much greater than the simple sum of their toxicity. Imagine the possibilities with as many as 17 different pesticides (or more) in a single meal.”

A joint Gothenburg and London universities study concluded that a mixture of chemicals can be far more toxic than a single chemical. The authors suggested developing measures to ensure effective assessment of these cocktails on human health and the environment.⁷

Spurred on by such findings, the European Commission has decided to investigate the effects of chemical mixtures. They claim chemical combinations have not been properly examined and are developing a new process that will assess the risks posed by these cocktails, which may lead to new legislations around chemical use.

However, here in New Zealand the cocktail effect has been carefully considered. John Reeve, principal adviser for toxicology at the MPI, says that the cocktail effect is real, but only comes into play when one of the ingredients is at high levels. When this occurs the damage done by the toxic ingredient allows other residues to have effects at much lower levels. However he points out that because New Zealand’s safety levels are so strict the cocktail effect isn’t likely to be able to come into play, so in general isn’t a concern for our produce.

John adds that the Ministry is quick to react to any new information, and says that because he is also a panel member at the World Health Organisation, he’s able to stay abreast of new toxicology information and help apply it to New Zealand very quickly.

The farmer’s view

One other point to consider is that New Zealanders work in agricultural and horticultural jobs which require the use of sprays. Agrichemical levels may be within acceptable levels in food, but the people who handle these substances in bulk can be exposed to much higher levels.

A 2009 New Zealand study by Dave McLean from the Centre of Pacific Health Research at Massey University looked at 225 cancer patients and 471 participants from the general public. The research found that those who worked in market gardens or nurseries using pesticides and other agrichemicals were four to five times more likely to develop leukaemia, with women being particularly badly affected. Crop growers were also shown to have a higher level of risk.⁸

And international evidence also points to the dangers of agrichemicals use. One example is a 2007 Canadian study conducted by a number of doctors. It concluded that there was strong evidence linking pesticide exposure to neurological diseases such as Parkinson’s disease, and found the risk of developing this disease was 70 per cent greater in those who had been exposed to even low levels of pesticide.⁹

What can I do?

On balance, New Zealand’s strict controls around agrichemicals mean there is little cause for alarm. However, if you choose to limit your exposure to such substances there are some simple steps you can take.

The Safe Food Campaign has identified a dozen fruit and vegetables that contain chemicals that are of the most concern (see ‘The dirty dozen’ below), so you can either choose to replace these with other varieties, or simply take more care to wash them before eating.

Buying organic produce is also a good way to avoid exotic chemicals in your food, and has added benefits for the environment and the people who produce our food. Unfortunately organic produce can be expensive, though the internet is useful for finding organic and spray-free produce at cheaper rates (see ‘Cheap organic food’ below).

And of course there’s always the DIY option. Wherever you live, and however large your garden, it’s possible to grow fruit and vegetables in your patch. Gardening is a bit of a commitment, but it’s worth it – you get spray-free seasonal produce that you can be sure is safe. There are many sustainable techniques for tackling bugs and disease in your garden. Websites like www.organicgardening.com have tips on growing without agrichemicals, and you can follow the organic gardening advice in this website.

The dirty dozen

These are the 12 foods that NZSFA testing found had the highest levels and greatest number of agrichemicals. Despite these results, none of the products exceeded residue safety levels.

(Supplied by the Safe Food Campaign)

Cheaper organic food

There are many services providing home delivery of organic food boxes throughout the country. For example in Auckland Naturally Organic offers food boxes from $19.95 (see www.naturallyorganic.co.nz). The Organic Connection in Wellington also delivers fruit and vegetable boxes to the door (www.organicconnection.co.nz). And in the South Island, Just Organic has a home delivery service as well, with fruit, vegetables and other organic goodies delivered to your door (see www.justorganic.co.nz).

The verdict

Green Ideas believes

• New Zealand’s strict controls on pesticide use are reassuring.
• Vegetables are proven to be good for you and shouldn’t be avoided.
• However, agrichemicals are often highly nasty substances and should be handled with great care in the garden or on the farm – and avoided where possible.
• Overuse of agrichemicals contributes to a farming culture that can be very damaging to our environment. Organic farming is a better way for New Zealand.
• The science behind agrichemical safety is evolving – Green Ideas will keep you informed.