Herbicides

Herbicides are widely used today as they are critical to no-till farming.

"Mounting concern over long term health risks and the skyrocketing cost of water treatment associated with pesticide contaminated tapwater in hundreds of midwestern towns has forged an unprecedented alliance between water utilities, engineers, and chemists, and environmental protection groups.

The new alliance recently called on pesticide companies that manufacture the weed killers, and the federal government, to take steps to make sure the chemicals do not get into water.

The collaboration, between groups that have often been at odds on tap water issues in the past, coincides with the release of a new Environmental Working Group report on pesticide contamination in Midwest tap water.

The study, the third in a series, reviewed the latest government testing data and unpublished water test results collected by the pesticide industry itself. EWG also worked with local activists in 12 communities to collect tap water samples in Illinois, Ohio, and Missouri, and submitted them to the University of Iowa Hygienic Lab for analysis.

The study found that over 10 million people in 374 communities across 12 states were exposed to at least one weed killer in their tap water. One pesticide, atrazine, was found in 96 percent of all surface water systems tested by the pesticide industry itself.

"Hundreds of midwestern communities are exposed, often unknowingly, to multiple pesticides in a single sample of tap water," said EWG analyst Brian Cohen, an author of the study. "We found that over 100 communities drink tap water contaminated by five or more pesticides," Cohen said, noting that ten pesticides were found in a single glass of tap water sampled in Williamsburg, Ohio, a suburb of Cincinnati.

"It is time to say, 'Enough is enough,'" said EWG vice president for research Richard Wiles, another author. "We estimate that at least 57,000 infants in the Midwest drink infant formula each year that is contaminated with atrazine and other cancer causing weed killers," Wiles said.

EWG's report emphasized that under a pesticide law passed unanimously by Congress last year, pesticide companies, for the first time, will have to take full account of human exposure to their products in water before pesticides can permitted for use on crops. The law requires EPA to certify that the dose of pesticides from food, water and all other sources meets tough standards designed to protect infants and children.

"Water suppliers throughout the Midwest find themselves in an impossible position," said EWG's Wiles. "When water comes through their intake pipes it has weed killers in it. They have no choice but to treat the water to reduce contamination or develop new, uncontaminated sources. It's costing millions of dollars across the midwest. And consumers have to pick up the tab," said Wiles. "This is completely unfair to water suppliers and water drinkers," added Wiles.


Types of herbicides:

1.Photosynthetic inhibitors ( 45%) act by preventing electron transfer between photosystem I and II.


2. Photosynthetic energy deviators compete for electron flow at the reducing end of photosystem I, accepting electrons that would otherwise have been passed on to ferrodoxin. It rapidly destroys plant cells but in the field sticks to clay so plants can be planted in a couple of days.


3. Inhibitors of chloroplast development, inhibit the formation of internal structures and block carotenoid synthesis


4. Uncouplers of respiration - for example they uncouple oxidative phosphorylation in the production of ATP. Are these really "only" herbicides? This group includes dinoseb ( LD 50 (rat)= 25 mg/kg; chicken = 40 mg/kg), DNOC


5. Growth regulators - activate rapid growth at the expense of photosynthesis. They result in too much shoot and root elongation but not in cell division. Auxin mimics

6. Inhibit the synthesis of aromatic amino acids and thus proteins. It includes glyphosate.


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