[Pollinator] Acute Insecticide Toxicity Loading increasing

[David Inouye]

DiBartolomeis, M., et al. (2019). "An assessment of acute insecticide 
toxicity loading (AITL) of chemical pesticides used on agricultural land 
in the United States." PLoS ONE 14(8): e0220029.
     We present a method for calculating the Acute Insecticide Toxicity 
Loading (AITL) on US agricultural lands and surrounding areas and an 
assessment of the changes in AITL from 1992 through 2014. The AITL 
method accounts for the total mass of insecticides used in the US, acute 
toxicity to insects using honey bee contact and oral LD50 as reference 
values for arthropod toxicity, and the environmental persistence of the 
pesticides. This screening analysis shows that the types of synthetic 
insecticides applied to agricultural lands have fundamentally shifted 
over the last two decades from predominantly organophosphorus and 
N-methyl carbamate pesticides to a mix dominated by neonicotinoids and 
pyrethroids. The neonicotinoids are generally applied to US agricultural 
land at lower application rates per acre; however, they are considerably 
more toxic to insects and generally persist longer in the environment. 
We found a 48- and 4-fold increase in AITL from 1992 to 2014 for oral 
and contact toxicity, respectively. Neonicotinoids are primarily 
responsible for this increase, representing between 61 to nearly 99 
percent of the total toxicity loading in 2014. The crops most 
responsible for the increase in AITL are corn and soybeans, with 
particularly large increases in relative soybean contributions to AITL 
between 2010 and 2014. Oral exposures are of potentially greater concern 
because of the relatively higher toxicity (low LD50s) and greater 
likelihood of exposure from residues in pollen, nectar, guttation water, 
and other environmental media. Using AITL to assess oral toxicity by 
class of pesticide, the neonicotinoids accounted for nearly 92 percent 
of total AITL from 1992 to 2014. Chlorpyrifos, the fifth most widely 
used insecticide during this time contributed just 1.4 percent of total 
AITL based on oral LD50s. Although we use some simplifying assumptions, 
our screening analysis demonstrates an increase in pesticide toxicity 
loading over the past 26 years, which potentially threatens the health 
of honey bees and other pollinators and may contribute to declines in 
beneficial insect populations as well as insectivorous birds and other 
insect consumers.


-- 
Dr. David W. Inouye
Professor Emeritus
Department of Biology
University of Maryland
College Park, MD 20742-4415
inouye at umd.edu

Principal Investigator
Rocky Mountain Biological Laboratory
PO Box 519
Crested Butte, CO 81224