Featured Research

from universities, journals, and other organizations

Breakdown Products Of Widely Used Pesticides Are Acutely Lethal To Amphibians, Study Finds

Date:
June 25, 2007
Source:
US Geological Survey
Summary:
The breakdown products (oxons) of the three most commonly used organophosphorus pesticides in California's agricultural Central Valley -- chlorpyrifos, malathion and diazinon -- are 10 - 100 times more toxic to amphibians than their parent compounds, which are already highly toxic to amphibians, according to recent experiments.

The breakdown products (oxons) of the three most commonly used organophosphorus pesticides in California's agricultural Central Valley -- chlorpyrifos, malathion and diazinon -- are 10 - 100 times more toxic to amphibians than their parent compounds, which are already highly toxic to amphibians, according to experiments conducted by scientists of Southern Illinois University, Carbondale, and the U.S. Geological Survey (USGS) Western Ecological Research Center.

"Since some of the parent pesticide compounds are already at concentrations sufficient to cause significant amphibian mortality in the Sierra Nevada, the higher toxicity of the breakdown products poses a serious problem," said Dr. Gary Fellers, coauthor of the study.

Dr. Donald Sparling, a research biologist and contaminants specialist at Southern Illinois University, and Fellers, a research biologist and amphibian specialist at the USGS Western Ecological Research Center in California, conducted laboratory tests to determine the acute toxicity -- the lethal dosage causing death in 96 hours or less -- of chlorpyrifos, malathion and diazinon, and their oxon derivatives on tadpoles of the foothill yellow-legged frog (Rana boylii).

Organophosphorus pesticides have been implicated in the declines of several amphibian species in the California Central Valley and in downwind montane areas, including the Cascades frog, California red-legged frog, mountain yellow-legged frog and the foothill yellow-legged frog, which inhabit foothill or montane regions east of the Central Valley.

More than 6 million pounds of active ingredient organophosphorus pesticides were used in California during 2004, the most recent year for which data are available. Researchers estimate that this accounts for about 25 percent of organophosphorus pesticide use nationwide.

Organophosphorus pesticides suppress an enzyme called acetylcholinesterase, which is essential for the proper functioning of the nervous system. Reduced levels of acetylcholinesterase cause neurological synapses to fire repeatedly and uncontrollably, leading to death, usually by asphyxiation as the animal loses respiratory control. Most pesticides of this group reach their greatest potencies when metabolized internally and converted to an oxon form in the liver. However, oxons can also be found in the environment, formed by bacterial decay of the parent pesticide.

For the laboratory experiments, tadpoles were raised from eggs collected from a stream in the California Coast Range, upwind of agricultural activities in the Central Valley and away from areas where significant quantities of pesticides are used. Test results indicated that chloroxon killed all tadpoles and was at least 100 times more toxic than the lowest concentration of the parent compound chlorpyrifos, which resulted in no mortality. Maloxon was nearly 100 times more toxic than malathion, and diazoxon was about 10 times more toxic than diazinon.

"Other data published in 2001 and new unpublished data show that these pesticides are widespread, even in pristine areas of the Sierra Nevada Mountains," Sparling said. "The combination of field and laboratory studies is revealing that organophosphorus pesticides are posing serious hazards to the welfare and survival of native amphibians in California."

The authors noted that amphibians inhabiting ponds in the Central Valley of California could be simultaneously exposed to two or all three of these pesticides and their oxons. "Because of this," said Sparling, "the potential for interactive effects of these chemicals needs to be explored."

Organophosphorus pesticides form the largest group of chemicals used in the control of pests, including invertebrates, vertebrates and, to a lesser extent, plants. Some 200 organophosphorus pesticides available in this class have been formulated into thousands of different products for use in agriculture, forests, gardens, homes and industrial sites.

The results of the laboratory experiments on the toxicity of three breakdown products were just published in the journal Environmental Pollution. The title of the article is "Comparative toxicity of chlorpyrifos, diazinon, malathion and their oxon derivatives to larval Rana boylii."


Story Source:

The above story is based on materials provided by US Geological Survey. Note: Materials may be edited for content and length.


Cite This Page:

US Geological Survey. "Breakdown Products Of Widely Used Pesticides Are Acutely Lethal To Amphibians, Study Finds." ScienceDaily. ScienceDaily, 25 June 2007. <www.sciencedaily.com/releases/2007/06/070623213748.htm>.
US Geological Survey. (2007, June 25). Breakdown Products Of Widely Used Pesticides Are Acutely Lethal To Amphibians, Study Finds. ScienceDaily. Retrieved September 1, 2014 from www.sciencedaily.com/releases/2007/06/070623213748.htm
US Geological Survey. "Breakdown Products Of Widely Used Pesticides Are Acutely Lethal To Amphibians, Study Finds." ScienceDaily. www.sciencedaily.com/releases/2007/06/070623213748.htm (accessed September 1, 2014).

Share This




More Plants & Animals News

Monday, September 1, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

We've Got Mites Living In Our Faces And So Do You

We've Got Mites Living In Our Faces And So Do You

Newsy (Aug. 30, 2014) A new study suggests 100 percent of adult humans (those over 18 years of age) have Demodex mites living in their faces. Video provided by Newsy
Powered by NewsLook.com
Washington Wildlife Center Goes Nuts Over Baby Squirrels

Washington Wildlife Center Goes Nuts Over Baby Squirrels

Reuters - US Online Video (Aug. 30, 2014) An animal rescue in Washington state receives an influx of orphaned squirrels, keeping workers busy as they nurse them back to health. Rough Cut (no reporter narration). Video provided by Reuters
Powered by NewsLook.com
Experimental Ebola Drug ZMapp Cures Lab Monkeys Of Disease

Experimental Ebola Drug ZMapp Cures Lab Monkeys Of Disease

Newsy (Aug. 29, 2014) In a new study, a promising experimental treatment for Ebola managed to cure a group of infected macaque monkeys. Video provided by Newsy
Powered by NewsLook.com
Killer Amoeba Found in Louisiana Water System

Killer Amoeba Found in Louisiana Water System

AP (Aug. 28, 2014) State health officials say testing has confirmed the presence of a killer amoeba in a water system serving three St. John the Baptist Parish towns. (Aug. 28) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins