Heavy metals testing: expect a fast-moving future

Toxic heavy metals (HMs) in our environment and foods represent “a severe issue” for humanity. Despite some success in reducing pollution, HMs’ toxicity, accumulation in biota, and inability to biodegrade in the environment means they continue to present a major global threat to both planetary and human health. Produced by natural emissions, industrial and agricultural activities, vehicles and waste, toxic HMs do not just contaminate most of the agricultural soils around the world, but are also “the primary cause of surface water quality degradation.” Moreover, their ability to mix with different environmental elements – like water, soil and air – means they become even more of a threat to humans, animals and their environment via routes such as the food chain. Although some HMs occur naturally, and even have biological significance as trace elements, exposure to their biotoxic effects can cause kidney, brain, liver, skin and cardiovascular toxicity, as well as reproductive problems, cell damage, and cancer. In June, Chemistry World reported on an Indian review paper linking uranium- and arsenic-contaminated drinking and irrigation water to high cancer rates in Malwa, “also known as the cancer belt of Punjab”. Meanwhile, computer analysis of pollution spread by dust in Nanjing, China, found “the risk of Zn (zinc) and Cr (cadmium)… to human health is relatively high, with the probability of carcinogenesis reaching 51.2 % and 50.2 % respectively.”

Taking a heavy toll

A global survey in The Lancet last year estimated that lead pollution alone caused 900,000 deaths in 2019, but said this was likely to be “a substantial undercount”, since new US data suggested that lead toxicity “could extend down to much lower blood lead concentrations than previously recognised.” It also calculated that more than 800 million children had blood lead concentrations above the US Centers for Disease Control and Prevention’s ‘concentration for intervention’. This, the report said, had “staggering” implications for children’s intellectual impairment and cognitive function that, in turn, triggered diminished economic activity and global economic losses of almost $1 trillion annually. Exposure to HMs also negatively affects global crop yields, through altered plant metabolism, growth reduction, and reduced biomass production.

Early regulation

The world began to get to grips with HM pollution in 1998, with the Aarhus Protocol on Heavy Metals, which committed participating nations to reducing emissions of cadmium, lead, and mercury to below 1990 levels. In 2012, the signatories agreed to more stringent emission controls, while a few years later the European Union also pledged to reduce the health impacts of air pollution by half by 2030, compared with 2005. As a result of these actions, EU cadmium, mercury and lead emissions fell by 39%, 51% and 49%, respectively, between 2005 and 2020.

Meanwhile, in the US, the Environmental Protection Agency seeks to protect the safety of drinking water from HMs through a system of maximum contaminant level goals (MCLGs) and enforceable maximum contaminant levels (MCLs). MCLGs represent the level at which no adverse health effects are expected, and so MCLs are set as close to them as is possible to achieve in real-world conditions. In the EU, maximum limits and target values apply to both water and air quality, while a wide range of regulations and directives also covers potential sources of heavy metal contamination including: apparel and textiles, batteries, cleaning products, electrical appliances, food contact materials, furniture, packaging, toys, and more.

New rules and pressures

Despite the range of regulations already in place, the appetite for reducing our exposure to HMs has grown fast across the globe in recent years.

In June, stricter food contamination levels came into force in China – including reduced lead limits for infant formula, dairy and meat products, and new maximum permitted levels of cadmium, mercury and arsenic. Meanwhile, the EU and UK introduced lower limits for arsenic in everyday rice-based food items, infant foods, fruit juices and salt.

Big changes are also happening in the US, where industry watchers have commented on the recent “aggressive movement ” from the Food and Drug Administration (FDA) towards monitoring and limiting heavy metals in foods. In its new draft guidance for the food industry, the FDA is proposing to slash permitted lead levels in apple juice from 50 ppb to 10ppb, and to 20 ppb for other juices. The move has also been accompanied by proposals to minimise lead levels in food intended for babies and young children, and to reduce inorganic arsenic content in apple juice. Commenting on the plans, food safety and public health specialist David Acheson warned the food industry to expect more demands from the FDA in future. “With scientific advances enabling increased detection and data, the agency is expanding its efforts to identify ways by which the levels can be reduced in foods,” he said, adding: “expect FDA to take a closer look at heavy metals and how you’re covering them in your food safety plan.”

The FDA’s initiative was announced in the wake of several high-profile news stories about heavy metals in American food which increased the pressure for change on regulators and manufacturers. Testing from the influential Consumer Reports organisation, which found 68% of the 50 baby products it tested had “worrisome levels of at least one heavy metal”, was followed by a 2021 House of Representatives committee report entitled ‘Baby Foods Are Tainted with Dangerous Levels of Arsenic, Lead, Cadmium, and Mercury’. The latter report made several  recommendations on reducing heavy metals in infant products – including mandatory testing and labelling, phasing out toxic ingredients, and introducing maximum levels for HMs.

Last December, Consumer Reports also issued research on cadmium and lead levels in 28 dark chocolate bars sold on the US market – finding that “For 23 of the bars, eating just an ounce a day would put an adult over a level that public health authorities… say may be harmful.” A study commissioned jointly by the US chocolate industry and the As You Sow advocacy group meanwhile found that, while cadmium finds its way into chocolate via the soil, cocoa beans become contaminated with lead post-harvest. The researchers also proposed a number of cadmium and lead reduction measures to the industry – an initiative that the leading confectionery manufacturer Hershey already seems to be taking on board. Speaking to reporters in March, the company’s chief financial officer Steve Voskiul said: “We would love to eradicate (lead and cadmium) completely and continue to look for opportunities in the process. Is there more we can do there?”

Consumer Reports meanwhile continues to petition the FDA to establish limits on heavy metals in all US foods, saying “No limits exist currently and there is no sign of any action from the FDA.” Could this perhaps be the next big regulatory change on the horizon?