In January 2012 officials from the US Food and Drug Administration (FDA), acting on a tip-off from soft drinks giant Coca-Cola, detained 26 shipments of orange juice products which were found to contain traces of the illegal fungicide carbendazim.

Approved for use in Brazil and several other countries to eradicate black spot, a type of mould that grows on orange trees, carbendazim is not permitted for use in citrus in the US. It is a suspected endocrine disruptor, meaning exposure to it in excessive quantities could interfere with the body’s hormone system.

Industry representatives argue that the FDA’s hardline stance is at odds with its own contention that any level of fungicide below 80ppb poses no health risk and that it should increase the permitted levels of carbendazim in frozen concentrated juice since the concentrate is diluted and would not exceed the limit in drinkable juice. Also, they have pointed out that the FDA did not consider the threat serious enough to recall any juice already on US store shelves.

The US Environmental Protection Agency (EPA), which approves fungicides and sets safety tolerances for residues, has approved the use of carbendazim on a variety of non-citrus fruit including apples, bananas, cherries and grapes, as well as other crops.

"The FDA remains adamant that any orange juice imports with measurable levels of fungicide will not be allowed into the US."

Unmoved, the FDA rejected calls from industry heavyweights including the US Juice Products Association and the Brazilian Association of Citrus Exporters, CitrusBR, to review its testing procedures, and remains resolute that any imports with measureable levels of fungicide – above ten parts per billion (ppb) – will not be allowed into the country.

"Carbendazim in orange juice is an unlawful pesticide chemical residue under the Federal Food, Drug and Cosmetic Act," explained FDA spokesperson Sebastian Cianci.

"The agency has been testing samples of orange juice shipments from all countries and manufacturers that offer such shipments for import into the US, as well as imported and finished product at domestic manufacturers."

The controversy has refocused attention on the ongoing debate over the safe use of pesticides, a term the EPA uses to describe not only insecticides but also herbicides, fungicides and other substances used to control pests. Here, we profile some of their uses and the associated risks.

Food for thought: protecting against harmful pesticides

The press may have squeezed every last drop of controversy from the stand-off between Brazilian and US juice producers and the federal government, but for foreign exporters the potential economic fallout is very real. Brazilian orange juice makes up about half of all US imports and meets more than a tenth of domestic demand.

"The FDA tests orange juice, as it does other major dietary items, as part of its routine pesticide monitoring programme," said Cianci.

"Based on the EPA’s conclusions from its risk assessment, consumption of orange juice with carbendazim at the low levels that have been reported does not raise safety concerns."

Despite such reassurances, the FDA continues to requisition orange juice shipments for testing. As recently as last month, federal officials detained and / or refused 30 shipments which tested positive for carbendazim, including 14 from Brazil, 12 from Canada, two from Costa Rica and one each from the Dominican Republic and Poland.

"Using the Xevo TQ-S mass spectrometer, Waters Corp has developed a ‘dilute-and-shoot’ method for the detection of carbendazim residues in orange juice."

The battle to protect the general public from pesticide contamination is being fought on two fronts: evolutionary research into newer, safer chemicals (the EPA permitted the limited use of carbendazim on citrus until 2009, after which more suitable fungicides were used instead – azoxystrobin, pyraclostrobin and trifloxystrobin are all thought to be effective for controlling black spot) and robust, industry-wide screening initiatives. In the UK alone, 4,000 food and drink samples are tested each year.

"Under the UK’s monitoring programme fruit and vegetables are tested for more than 250 different pesticides," a spokesperson for the UK Chemicals Regulation Directorate (CRD) said.

"Different pesticides are used on different crops and foods in different parts of the world, depending on pest and disease pressures as well as what pesticides are legal in the country where the food is being grown."

An agency of the Health and Safety Executive (HSE), the CRD is overseen by a scientific advisory committee, the Defra Expert Committee on Pesticide Residues in Food (PRiF).

"A pesticide will only be approved if any residues that remain are below the levels that may affect public health," the spokesperson continued. "The approval process will also consider whether residues will become concentrated or diluted when treated crops are eaten by animals, and the levels which will be present in produce coming from animals, including meat, eggs and milk."

Across the Atlantic, the US Government is sufficiently concerned about pesticide contamination in food to include it within the scope of the 2011 Food Safety Modernization Act (FSMA).

"Under the forthcoming FSMA regulations, food facilities will be required to implement a written preventive controls plan for hazards that could affect food safety," said Cianci. "The FSMA specifies that pesticides must be included in a facility’s evaluation of potential food safety hazards."

At the time of writing, the EPA is assessing the potential effects of three pesticides, oryzalin, pendimethalin and trifluralin, on Pacific salmon and steelhead.

Food testing techniques: multiresidue analysis for pesticides

In most countries, legislation imposes strict maximum residue limits (MRLs) for pesticide residues in food products. With more than 1,000 pesticides currently in use worldwide, the challenge for laboratories is to develop multiresidue pesticide analysis techniques which can screen an ever increasing spectrum of chemicals in a single analysis over a shortened run time.

In the US, scientists at Waters Corp, a Massachusetts-based company specialising in analytical technology, have responded by using innovative mass spectrometry (MS) techniques.

MS works by ionising chemical compounds and can be used to establish the masses of particles, the elemental composition of a sample or molecule, and the chemical structures of peptides and chemical compounds.

Using the ultra-high sensitivity Xevo TQ-S mass spectrometer in tandem with liquid chromatography (LC) technology, Waters has developed a simple ‘dilute-and-shoot’ method for the detection of carbendazim residues in orange juice at concentrations below 10ppb. The LC-MS system eliminates sample preparation, resulting in high analysis throughput and simplified method development and optimisation.

Pesticide alternatives: hungry for change

With world demand for food set to increase by 50% by 2030, a collaborative effort involving government regulators, industry and academia is required to ensure that large-scale food production evolves to meet the needs of an ever-expanding global population – and that includes alternatives to often expensive, highly toxic and carbon-intensive pesticides.

"Under the UK’s monitoring programme fruit and vegetables are tested for more than 250 different pesticides."

One such innovation – a genetically modified (GM) wheat which emits odour to repel aphids – is being developed by scientists at Rothamsted Research in Hertfordshire, UK. The wheat variety releases a chemical known as E-beta-farnesene, which is naturally produced by aphids to alert each other of imminent danger.

Aphids are a major pest problem for cereal crops across northern Europe, causing £80m-£120m worth of losses to UK farmers every year. The wheat is considered to be the world’s first GM crop which repels pests instead of killing them, as well as lowering their likelihood of developing immunity to pesticides. Predictably, the project has attracted criticism from environmentalists.

"Insects adapt quickly," Pete Riley, from the anti-GM campaign group GM Freeze, told the BBC, "and if you expose them to this pheromone for any length of time they’re likely to get habituated to it and ignore it. There are also safety concerns about whether this gene will change the chemistry of wheat in ways we can’t predict".

Undeterred, the scientists continue their work and by exploiting the natural defences some plants have evolved, they may yet succeed in boosting production of a key foodstuff in an ecologically friendly way.