Below are the pesticides with established tolerances (residue limits for pesticides used in the U.S. or by countries exporting to the U.S.) for onions. While not all the pesticides on the list are applied to all onions, there is no way to tell which pesticides are applied to any given piece of conventional produce on your store shelf. You may consider talking to the farmers at your local farmers market about the pesticides they use, but eating organic is the only way to know for sure.
California Farmworker Poisonings, 1992–2010: 36 reported (CA acreage: 102,800). These poisoning incidents only represent the tip of the iceberg because it only reflects reported incidents in one state. It is widely recognized that pesticide incidents are underreported and often misdiagnosed.
Pesticide Tolerances —Health and Environmental Effects: The database shows that while onions grown with toxic chemicals show low pesticide residues on the finished commodity, there are 63 pesticides with established tolerance for onions, 27 are acutely toxic creating a hazardous environment for farmworkers, 58 are linked to chronic health problems (such as cancer), 15 contaminate streams or groundwater, and 57 are poisonous to wildlife.
Pollinator Impacts: In addition to habitat loss due to the expansion of agricultural and urban areas, the database shows that there are 20 pesticides used on onions that are considered toxic to honey bees and other insect pollinators. For more information on how to protect pollinators from pesticides, see Beyond Pesticides' BEE Protective webpage.
(A = acute health effects, C = chronic health effects, SW = surface water contaminant, GW = ground water contaminant, W = wildlife poison, B = bee poison, LT = long-range transport)
All tolerance data is based on the Environmental Protection Agency's Tolerances by Commodity, Crop Group, or Crop Subgroup Index (last updated July 2009). For more information, see our Methodology page.