A class of insecticides linked to colony collapse disorder in bee colonies has been detected in US drinking water for the very first time. The amounts are admittedly low, but scientists aren't sure if long term exposure to these chemicals, known as neonicotinoids, are a threat to human health.
Researchers from the US Geological Survey (USGS) and the University of Iowa have detected minute traces of a widely used insecticide in samples taken from two water treatment facilities in the state of Iowa. The samples showed low levels of neonicotinoid chemicals after treatment. There are currently no regulatory limits in place for these substances in the United States, and scientists are woefully ignorant of the human health impacts posed by frequent, low level exposure -- although that's not necessarily a reason to panic.
Widespread use of neonicotinoid insecticides began in the 1990s, and it represented an innovative step forward in the battle against pests. The chemicals could be applied directly as a seed coating (allowing its noxious effects to last longer) and it was supposedly harmless to non-insects. Neonicotinoid chemicals wreak havoc in an insect's brain, causing its nervous system to shut down. After exposure, an insect enters into a short-lived phase of agitated hyperactivity, but it eventually becomes paralysed and dies. Bad for bugs, great for farmers.
But as time has passed, we've learned that neonicotinoids are also bad for the environment, in part due to ecological ripple effects. These chemicals have been linked to declining bee populations, leading the European Union to place a moratorium on their use. In 2014, a study linked neonicotinoid use to the decline of insectivorous birds, as a result of having less to eat. There's also concern that neonicotinoids are trickling into our water systems. Two years ago, the USGS found neonicotinoid chemicals in water samples collected from nearly 50 different rivers and streams in the United States.
And in the latest development, described in the journal Environmental Science and Technology Letters, neonicotinoids are passing through water treatment plants and entering America's water supply. Despite treatment, the water still contained traces -- albeit very small ones -- of three main neonics chemicals. In a facility that serves Iowa city, the carbon filtration system removed 100 per cent, 94 per cent and 85 per cent of the neonicotinoids clothianidin, imidacloprid and thiamethoxam, respectively. That represents 0.24 to 57.3 nanograms of nanograms of individual neonicotinoids per litre, which is like a single drop of water plopped into 20 Olympic-size swimming pools.
"At this point in time, these results don't indicate any violation of the system, we are trying to bring these contaminants to light more than saying this is or isn't a safe level," said study co-author Gregory LeFevre in BBC News. The carbon filtration system is actually working quite well; the larger issue is our knowledge gap in terms of the health risks.
Surprisingly, or perhaps unsurprisingly, the US Environmental Protection Agency has no regulatory limits on the use of these substances. The EPA monitors contaminants in water, but it doesn't consider neonics a threat. Previous studies have shown that exposure to high concentrations over a brief period results in "low rates of adverse health effects" for humans. More studies are needed to determine whether long-term, low level exposure to neonicotinoids might be harmful. As George Washington University public health research told the Washington Post, the new finding "provides further evidence that neonicotinoid pesticides are present in our daily environments. From a public health standpoint, this issue clearly needs better attention."
If these scant levels are deemed a problem, then water treatment facilities will have to be modified accordingly. Either that or farmers will have to employ anti-insect strategies that don't involve neonicotinoids.