Trifluralin

Trifluralin was introduced in 1963 and is a dinitroaniline herbicide used primarily to prevent emergence of annual grasses and broadleaf weeds in soybeans, cotton, and sunflowers [1]. About 10–15 million pounds are applied annually in the US. It is extremely volatile — up to 90% of applied trifluralin can volatilize within weeks of application, traveling long distances from application sites via the atmosphere [2]. This volatility makes trifluralin ubiquitous in air samples across agricultural regions and contributes to its detection in remote environments including the Arctic. Despite volatilizing from soil surface, trifluralin that is incorporated into soil is more persistent and can contaminate groundwater [3].

Agricultural workers who mix, load, and apply trifluralin have the highest occupational exposures through skin contact and inhalation [1]. Community members in agricultural areas breathe trifluralin during and after application due to its volatility. Dietary exposure from residues on treated crops is monitored by USDA [2]. Groundwater contamination near agricultural fields is documented in some regions. Fish in agricultural waterways accumulate trifluralin from sediment [3].

Trifluralin is classified as a possible human carcinogen (IARC Group 2B), with evidence for lymphomas and kidney tumors in animal studies [1]. It is bioaccumulative in aquatic organisms — its octanol-water partition coefficient indicates moderate lipophilicity and accumulation potential. Trifluralin inhibits tubulin polymerization (the same mechanism as it kills plants — disrupting cell division), which has implications for rapidly dividing mammalian cells as well [2]. The atmospheric volatilization and long-range transport means trifluralin exposure occurs in communities hundreds of miles from application sites [3].

Agricultural workers who apply trifluralin without adequate PPE face the highest exposures [1]. People who live near soybean and cotton production areas face ambient air exposure during application seasons [2]. Frequent consumers of locally caught fish from agricultural waterways in high-use regions may have dietary exposure.

Agricultural applicators: wear coveralls and a NIOSH-approved respirator during mixing and application [1]. Incorporate trifluralin into soil immediately after application to reduce volatilization. Support IPM practices that reduce herbicide use [2]. Choose organic versions of crops treated with high herbicide rates when possible [3].