Thursday, July 24, 2008

EPA reconsiders ban on MSMA

The need to find lees harmful herbicides/weed controls have grown expediently in this decade alone. The market is demanding environmentally friendly pest management solutions out of a concern for the environment (water quality, non-target flora/fauna) and human health. Therefore we will see many older products go and newer products make their way into the market place.

There is a lot of green washing and confusion out there, by people on both sides of the argument to ban pesticides. Go Fore The Green wants to know what you think about this latest story from Golfdom Magazine. Green Wash? or Greener Solution? Check out the article from ES and T, it is pro-ban, but very good.

What would Mark Twain say about MSMA? That the rumors of the embattled herbicide's demise have been greatly exaggerated.

Golf turf expert Fred Yelverton, a professor of crop science at North Carolina State University, is saying the same thing. Yelverton, who spoke at the Warm-Season Weed Control Symposium sponsored by Bayer Environmental Science July 9-10 in Newport, R.I., reported that the Environmental Protection Agency might not ban MSMA after all.

MSMA, classified as an organic arsenical, is used for grass weed control in bermudagrass and zoysiagrass and on some cool-season turfgrasses. It is used for postemergence control of goosegrass, crabgrasses and dallisgrass in bermudagrass.

In 2006, EPA announced it would cancel reregistration of any pesticides containing MSMA. Arsenic levels left by MSMA "raise a concern for cancer risk," EPA officials concluded.

But nearly two years later, MSMA is still around.

"We thought EPA was going to ban it six months ago," Yelverton says, "but it has new life. What are the chances of keeping it? I would say 50-50. The final decision could be tomorrow, or it might be six months from now."

EPA is taking a second look at MSMA because the organization admits it acted too quickly to dismiss it.

"There are some people who believe the EPA was under political pressure to ban some products," Yelverton says. "Because MSMA was not used in many commodities, it was an easy target."

The EPA has agreed to take a second look at MSMA for two reasons, Yelverton says. First, it underestimated the need for MSMA, especially in the golf course industry. Second, EPA admits it might have overestimated the risk of organic arsenic and MSMA's contribution to environmental inorganic arsenic levels. Yelverton points out that organic arsenic is a naturally occurring element.

"You can find it anywhere," he says. "We're all exposed to it every day. It is added to chicken feed, for example. So when you eat chicken, you're exposed to it."

The problem is that people, including environmentalists, associate MSMA with inorganic arsenics, which are very toxic. "But organic arsenics are not," he adds.

Yelverton says there's a conversion rate between organic arsenicals to inorganic arsenic, but it is very low. He says the EPA has now realized this.

Yelverton points out that research shows MSMA has low mobility and strongly absorbs into soil.

"It doesn't leech into the ground water," he says. "From an environmental standpoint, it's safe."

Heres a video from the event

Okay, so thats one side, heres another from ES and T, they makes some undisputable points, give it a read.

Science News – February 9, 2005

Common Arsenical Pesticide under scrutiny

Golfers can thank monosodium methanearsonate (MSMA) for flawless, weed-free fairways, but experts are questioning whether the arsenic-containing pesticide is safe for the environment and human health. New research reveals that, despite industry claims, MSMA applied to golf courses with certain types of soil degrades to toxic inorganic arsenic, which leaches into groundwater. A separate study has documented that MSMA can move through wildlife food chains. The news comes as Canada and the United States are re-evaluating registrations for MSMA.

According to the U.S. EPA, MSMA “can reasonably be anticipated to cause cancer in humans” and is converted in the environment to inorganic arsenic, a known human carcinogen. About 4 million pounds of MSMA is applied every year to golf courses and cotton fields in the United States to control weeds. The pesticide has been banned in India and Indonesia.

Concerns about the fate and transport of MSMA led to a collaborative study between Yong Cai and his colleagues at Florida International University and George Snyder, John Cisar, and their colleagues at the University of Florida. They dosed an experimental golf green at the University of Florida with MSMA and monitored the soil and the water percolating through the soil. “Presumably due to microbial activity in the soil, MSMA was transformed to As(V), As(III), monomethylarsonic acid, and dimethylarsinic acid, with As(V) being the major form,” Snyder says. After 14 weeks, almost 20% of the arsenic in the MSMA percolated below the root zone of sandy soils in the form of inorganic arsenic, Cai says. The more clay there is in the soil, the more arsenic is retained, he notes. The study has been submitted to a peer-reviewed journal.

Some industry scientists have criticized Cai’s study, saying that the apparatus used to collect leachate promotes the growth of bacteria, which boost the transformation of MSMA beyond what would be expected in the soil. However, Cai and Snyder’s findings are corroborated by a Florida Department of Environmental Protection (FDEP) study that found contamination after examining 65 groundwater samples from 7 different golf courses where MSMA was legally applied ( Shallow monitoring wells revealed that 86% of the samples contained more than 10 micrograms of total arsenic per liter, which is the new groundwater standard in Florida. In areas with high water tables, just a single application of MSMA is likely to render the underlying groundwater out of compliance with the new standard, the study says.

FDEP has recommended restricting the use of MSMA in vulnerable areas with sandy soils and high water tables. Florida’s Department of Agriculture and Consumer Services (FDACS) has asked companies that sell MSMA in the state to conduct further field tests, says Dennis Howard, chief of the bureau of pesticides at FDACS. Representatives from these companies have maintained that MSMA is quickly adsorbed into soil and not easily released, he says.

Meanwhile, in Canada, the permit to inject pine trees with MSMA to curb outbreaks of mountain pine beetles has expired, and the manufacturer, United Agri Products Canada, Inc., has withdrawn MSMA from the Canadian market. Agencies are also evaluating work from the Canadian Wildlife Service, which shows that woodpeckers feeding on bark beetles in treated trees had 4–7 times the level of arsenic in their blood than species that don’t feed on the beetles.

Although organic forms of arsenic were once thought to be less toxic than inorganic arsenic, new research on the metabolism and toxicity of both organic and inorganic arsenic has changed that view, says Mirek Styblo, biochemical toxicologist at the University of North Carolina, Chapel Hill. He says that human cells metabolize As(V) to As(III) and trivalent methylated forms—monomethylarsonous acid and dimethylarsinous acid. He and others have shown that all the trivalent forms, including methylated ones, are genotoxic and more toxic than the corresponding pentavalent forms.

“But we’re lacking data on the chronic toxicity of methylated arsenicals, including the trivalent and pentavalent forms,” Styblo says. “If [Snyder and Cai] have really shown that MSMA is demethylated, that is very important because it means that arsenic could end up in drinking water,” he warns.

MSMA does not cause cancer in animal studies and is safe if used properly, says Barbara Beck, director of health sciences at Gradient Corp., a consulting firm. If it is ingested, 95% is converted in the gut to monomethylarsonic acid, which is rapidly excreted, and the remainder is metabolized to dimethylarsinic acid, she adds.


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