By: Heather Williams
Pesticides. Some say a necessary evil. They help protect crops and make the cost of farming more profitable by reducing loss. But what are the long-term effects? A recent Swiss study examined the impact of a particular pesticide, neonicotinoid, on bees and the presence of this pesticide in the honey we eat. What does this mean for the pollinators responsible for maintaining our ecosystems and food sources? What does this mean for us, the consumers of the honey they produce? The effects are both widespread and long-term.
The pesticide neonicotinoid, first introduced in the mid 1990’s, is used globally. Since introduction, it is the fastest growing and used class of insecticides in the United States. According to publicly available data as of 2011, about 3.5 million pounds of this class of pesticide is applied to nearly 127 million acres of agricultural crops. While widely used, recent studies have indicated the negative impact the chemical has on the nervous system of bees. In recent years the efforts to reduce the use of these pesticides, though the damage has already been done.
Effects of Neonicotinoid on Bees
Neonicotinoid is a common type of insecticide. While it affects harmful insects that decimate crops, it also affects the beneficial pollinators responsible for the growth of crops, plants, and ecosystems. This chemical not only impairs bee brain function but slows the growth of bee colonies. While Bayer AG and other manufacturers reject the correlation of the increased use in this particular class of pesticide and an alarming 90% decline in pollinator population, beekeepers indicated that 13 of colonies in the second quarter of this year were stressed by pesticides.
May Berenbaum, head of the entomology department at the University of Illinois and a Nation Medal of Science recipient explains his bee losses seem to be attributed to the location of the hives. He explains that it may be affected by farmers improperly spraying pesticides and the relative proximity to the hives. May explains, “It’s really tricky” to sift through the factors behind bee death. “Maybe it’s pesticides, maybe it’s not. But when I eliminate everything else, it’s a distinct possibility.”
Additional studies funded in part by Bayer CropScience and Syngenta AG has linked the neonicotinoid class of pesticide to poor reproduction and shorter lifespans in both European and Canadian bees. This combination contributes to hive collapse and decrease in the overall number of pollinators available to do the important job of maintaining the eco-diversity of plant life.
The U.S. Environmental Protection Agency is currently reviewing the use of neonicotinoids and proposing bans on spraying them, along with several dozen other pesticides in fields where bees have been brought in to pollinate a crop.
Presence of Neonicotinoid Pesticides in Honey
A Swiss study published this month examined the presence of neonicotinoid pesticides in honey. While the neonicotinoid compounds have been detected at levels that are considered safe for human consumption, the compound is still present. This occurrence demonstrates the inundation of the pesticide and the impact on bees, despite recent efforts to decrease the use of this class of pesticide.
The study analyzed 198 honey samples from different hives across the world. A staggering 75% of all samples tested contained at least one of the five compounds of interest. Acetamiprid, clothianidin, imidacloprid, thiacloprid, and thiamethoxam. Almost half of the honey samples contained two or more of the tested compounds (at 45%). An astounding 10% of the honey samples tested contained four or five of the compounds. This data indicates that bees across the world are exposed to neonicotinoids in their food.
“Our results confirm the exposure of bees to neonicotinoids in their food throughout the world,” researchers wrote. “The coexistence of neonicotinoids and other pesticides may increase harm to pollinators.”
Samples from all continents, except Antarctica, were included in the study. Of all continents examined, North America had the highest proportion of neonicotinoid contaminated honey samples with 86% containing the chemical. Asian samples had 80% with the compound followed by Europe at 79%.
Spread of Neonicotinoid
The nature of the chemical is that it is taken up into the roots or leaves and brought into other parts of the plant. This allows all parts of the treated plant to be toxic to insects. This activity has a wider reach than just the plant. Studies from the U.S. Geological Survey has found neonicotinoid contamination in surface and groundwater, which may later become a source of drinking water. In fact, three-quarters of the sites monitored in nine different rivers in the Midwest were positive for clothianidin, one-half were positive for thiamethoxam, and one-quarter were positive for imidacloprid.
Limited testing from the U.S. Department of Agriculture has found the chemical in fruits and vegetables rather than on the surface, where it cannot be removed from the produce.
Effects of Neonicotinoid in Humans
At the current rate, the neonicotinoid class of pesticides are below harmful levels for humans at this time, this statistic could change leaving honey out of many people’s diets. Studies have proven that these chemicals have an impact on bees’ nervous system and growth. But what are the effects on humans?
The European Food Safety Authority conducted a study with cell cultures and rodents. Two neonics (from the neonicotinoid class of pesticide) – imidacloprid and acetamiprid, were potentially linked to impairing the developing human nervous system. Studies have shown that exposure to imidacloprid during pregnancy and lactation created persistent changes in brain structures and poor behavioral test performance in offspring of exposed mother.
The neurological affects are not surprising. The pesticide was design to target the insect nervous system. This seems to be the same affect the chemical has on animals. In animals, it binds to a receptor on nerve cells that generally binds to acetylcholine. This is normally fatal in insects, but in people this receptor has additional functions including brain formation during fetal growth, muscle contraction, learning, and the ability to pay attention. As a result, excessive exposure during pregnancy and lactation could result in autism and other neurological issues.