Emerging Pesticides: Trifluralin

A recent ad campaign for Preen, a weed preventer comprised of ~1.5% trifluralin (2,6-dinitro-N,N-dipropyl-4-(trifluoromethyl)benzenamine or α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine) caught our attention in a market where glyphosate is a dominant herbicide. Trifluralin is a pre-emergent dinitroaniline herbicide that was first approved for use by the US EPA in the early 1960s and has been assigned CAS Number 1582-09-8.

The EPA Fact Sheet (http://www.epa.gov/osw/hazard/wastemin/minimize/factshts/triflur.pdf) does not offer extensive information about Trifluralin, but Trifluralin was banned for all uses in Europe in 2009 (http://archive.pic.int/CH/Demo/embed/view_displayFRA.php?id=1186&back=viewB_FRAchems.php?sort=chemical) because of concerns about its:

• high risk for aquatic organisms (especially fish)
• high persistence in soil
• high potential for bioaccumulation
• potential for long-range transport via air

While relatively nontoxic In acute exposures to mammals and birds, trifluralin is classified by the US EPA as a possible carcinogen and by the Illinois EPA as a probable endocrine disruptor.

Trifluralin has a very high toxicity to fish and other aquatic organisms, with LC50s in the sub-100 ppb range. Although considered persistent, its affinity for soils, coupled with its relatively low solubility in water reduces concerns for transport.

CIL has offered deuterated trifluralin since the 1990s. The part numbers for the quantitative standards are: