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Re: E-M:/ Reward, Aquathol - Hydrothol-191

Enviro-Mich message from koseks@deq.state.mi.us (Sandra Kosek)

Hi Andrea (and Enviro-Mich),

My group is responsible for reviewing the toxicity of substances added to 
water for various types of treatments, including aquatic herbicides. The 
actual permits are issued by Land and Water Management Division, so if you 
want specific details of the permit for this lake call (517) 373-8000 
(that's their general number, you'll be forwarded to the appropriate people).

Specific toxicity info for Aquathol: this substance is a dimethylalkylamine 
salt derived from coconut oil. It degrades in fish tissue and water to 
natural substances in 3-10 days and has not been found to bioaccumulate. It 
is relatively non-toxic to aquatic organisms, with a no-effect level of 
49-170 mg/l (ppm). The non-drinking water human life cycle safe 
concentration is 85 mg/l (drinking water not calculated). In comparison, the 
highest dosage used for weed treatment is 5 mg/l. The fish consumption 
warning is based on old data; the company that makes it (ELF Atochem) has a 
couple of recent studies that show this warning is not necessary and they 
are trying to get it removed.

As weed treatments go, this one sounds pretty innocuous to me. The most 
harmful effect noted in our files is the possibility of reduced oxygen 
levels in the water due to large amounts of decaying weeds. This might kill 
a few fish if the lake is large, deep, and has LOTS of weeds.

I would just follow the posted directions and not worry about this one. 
Considering that it is an herbicide, it makes sense to not water your lawn 
with it! I wouldn't worry about your dogs, just don't encourage them to get 
in the water for a day or two right after the treatment.

As a final comment, if you or anyone else would really like to get into the 
issue, you may want to investigate why the plants are occurring at nuisance 
levels in the first place. This is usually due to moderate levels of 
nutrients in the water (high levels lead to excessive algae growth). 
Ironically, lakes with weed problems usually have good water quality! But it 
takes excellent water quality, which is not always attainable due to soil 
type and climate, to get nutrients down below levels that allow aquatic 
plants to grow.


>My parents own a cottage on Lake LeAnn, near the Irish Hills area.  Every 
>year, for as far back as they've owned it (12 years) - I can remember 
>a company coming in and "treating" the lake to rid it of excessive weeds.  
>The lake is treated with:  Reward, Aquathol-Hydrothol-191  Does anyone 
>have any accurate information on the real effects of these herbicides on 
>the lake ecosystem.  The flyer they put up includes the following 
>Lake treated June 9, 1997
>Do not use treated water for swimming or bathing until 		June 10
>Do not use treated water for crop irrigation, household
>uses or animal watering until					June 16
>Do not use treated water for lawn irrigation until		June 16
>Do not consume fish caught from treated waters until		June 12
>The DEQ has provided a permit to do this and the herbicides have been 
>registered by the EPA. It goes on to say that the possibility of impacts 
>on non-target fish and other organisms is minimal.
>My father fishes the lake regularly and I have two Weimaraners who love 
>to fetch buoys from the water (consequently gulping large amounts of 
>water in the process).  I am concerned that we might not be getting the 
>full story.  How does this stuff break down, does it accumulate in the 
>fish, etc.?
>				 Andie Kinnie
>	  National Consortium for Environmental Education & Training
>		        email ~ andrea@eelink.umich.edu
>      		        phone ~     (313) 763-1312
>			web   ~ http://eelink.umich.edu			

Sandra Kosek
Aquatic Biologist

Surface Water Quality Division
Michigan Department of Environmental Quality
P. O. Box 30273
Lansing, Michigan 48909

phone: (517) 335-3307
fax: (517) 373-9958
email: koseks@deq.state.mi.us

MDEQ website: http://www.deq.state.mi.us

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