Definition of simazine:
Simazine belongs to the same class of herbicides as atrazine. It is widely used as a selective herbicide to control most annual grasses and broadleaf weeds before they emerge or after removal of weed growth.
This is the common definition for simazine, other definitions can be discussed in the article
In the USA, an estimated 2000 to 2500 tons of simazine are applied to agricultural crops (mainly on corn, fruits and nuts) each year, and an additional 500 tons are applied for nonagricultural uses. It mainly enters the marine environment through run off from application sites.
Simazine is moderately soluble (3,5 mg/L) and has a low tendency to be absorbed to organic matter or into the soil, although it can adsorb to clay particles. Therefore simazine is highly mobile and can leach into ground water systems. It has low volatility, therefore losses of simazine by evaporation into the atmosphere are expected to be rather low. According to laboratory studies simazine is persistent and able to persist into the environment for months (half-life of 90 days).
Simazine has a low potential to bioaccumulate in fish and is therefore not expected to biomagnify through food chains.
Simazine is moderately toxic to aquatic animals. Acute toxicity can in some fishes be caused by concentrations above 3 mg/l, although for most species it takes simazine concentrations above 100 mg/l. Oysters die at concentrations above 3,7 mg/l. Algae are highly affected by low concentrations of the herbicide as short exposure concentrations of only 6 µg/l can be lethal to some species.
The maximum concentration measured in an UK estuary was 0,39 µg/l.
Environmental standards and legislation
Included in the water framework list of priority substances
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