Those Pesky Pesticides
Dr. Rebecca Lyons talks rogue estrogen-imitating pollutants and the shielding effect of the Sierra Crest
At the Tuesday, May 16 installment of the Sierra Nevada Aquatic Research Lab (SNARL) Spring Lecture Series, Dr. Rebecca Lyons of the University of Redlands presented research on a particularly sinister compound found in most pesticides. A physical chemist by trade, Lyons has spent the last 5 years studying how 4-nonylphenol, a compound that mimics the most common form of estrogen when it gets into the endocrine system of macroinvertebrates and small mammals, is carried via dust and wind. Once 4-nonyphenol enters an organism’s blood stream, it binds with compounds that would otherwise bind with estrogen, a hormone produced naturally by the body. Estrogen is involved in reactions that facilitate reproduction, growth, and other essential bodily processes, so when it gets ousted from those reactions by 4-nonylphenol, it wreaks havoc. It’s been proven to inhibit reproduction in vertebrates such as birds and fish when found in concentrations as low as 3 micrograms per liter of water.
According to Lyons, 4-nonylphenol starts out as nonylphenol polyethoxylate, a synthetic compound used to give pesticides, industrial detergents, sun screens and lotions a consistent texture. “It constitutes about 10 percent of all pesticides by volume, but it’s not the active ingredient in any of these products, so manufacturers are not required to report it on the label,” said Lyons. Over time, nonylphenol polyethoxylates degrade into 4-nonylphenol.
Lyons and her team have tested countless water sources throughout the state, and have had trouble finding water that is not contaminated with 4-nonylphenol. Knowing the Sierra is an essential water source for Southern California communities, Lyons began studying the way the compound is spread. “In California, we have a very impressive physical barrier to pollutant travel,” said Lyons, referring to the Sierra Crest. “We also know that Fresno, Kern, and San Joaquin Counties use the most pesticides of any counties in the state, and that Mono and Inyo Counties use the least.”
Lyons and her team have collected 5 years of data, sampling surface water, soil, and snow at various locations along the Crest. In most cases, they found higher concentrations of the toxic compound as they moved farther from the Crest. “We found that there was some topographical shielding,” said Lyons, whose team found that, although 4-nonylphenol is present in Eastern Sierra streams, reservoirs, and soil, most of the particles being carried eastward from the central valley are deposited in Nevada, bypassing the eastern slope of the Sierra. This was due in part to the fact that 4-nonylphenol was found in much higher concentrations as dust than in snow, perhaps because it is a non-polar, or water-averse, molecule.
