2,4-Dichlorophenoxyacetic Acid (2,4-D)

2,4-Dichlorophenoxyacetic acid is a common systemic pesticide/herbicide used in the control of broadleaf weeds. It is one of the most widely used herbicides in the world, and is the third most commonly used herbicide in North America. 2,4-D is a synthetic auxin (plant hormone), and as such it is often used in laboratories for plant research and as a supplement in plant cell culture media such as MS medium. Some preparations of 2,4-D are contaminated with dioxins due to the manufacturing process. Tetrachlorodibenzo-p-dioxin (TCDD) is classified as "carcinogenic to humans" by International Agency for Research on Cancer. Contamination is predominantly of the type with 2 or 3 chlorine atoms. Another form of dioxin, 2,7-dichlorodibenzo-p-dioxin (2,7-DCDD) was found to be equipotent to dioxin TCDD in its toxic effect on the immunity of mice.