Chlorophenoxy herbicides

TCDD is the most potent inducer of chloracne. This has been well known since the accident in Seveso, Italy, in 1976 in which large amounts of TCDD were distributed in the environment subsequent to an explosion in a factory that produced a chlorophenoxy herbicide, 2,4,5-T. TCDD is an impurity produced during the production of 2,4,5-T. The most common long-term effect of TCDD exposure was chloracne. Exposed individuals also suffered increased excretion of porphyrins, hyper-pigmentation, central nervous system effects, and liver damage and increased risk of cancer was a long-term consequence of the exposure. In addition to TCDD, polychlorinated biphenyls (PCBs), polychlorinated dibenzofurans, and polychloronaphthalens cause chloracne as well as other effects typical of TCDD. 7i... 

Pierotti, C., Deal, C., and Derr, E. Activity coefficient and molecular structure, Ind. Chem. Eng. Fundam., 51 95-101, 1959. Pignatello, J.J. Dark and photoassisted Fe -catalyzed degradation of chlorophenoxy herbicides by hydrogen peroxide. Environ. 

Very few human data are available to assess the long-term effects of amitrole. In a small-cohort study of Swedish railroad workers, there was a statistically significant excess of all cancers among those exposed to both amitrole and chlorophenoxy herbicides (6 deaths vs. 2.9 expected) but not among those exposed primarily to amitrole (5 deaths vs. 3.3 expected). ... 

Chlorophenoxy herbicides 2,4-D 2,4,5-T Bipyridyl herbicides Paraquat, diquat... 

The chlorophenoxy herbicides, 2,4-dichlorophenoxyacetic acid (2,4-D) and 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), were used in defoliating operations... 

Chlorophenoxy herbicides (oeeupational exposures to) 4-Chloro-ort/io-phenylenediamine 4-Chloro-meta-phenylenedi amine Chloroprene... 

D (see also Chlorophenoxy herbicides Chlorophenoxy herbicides, occupational exposures to)... 

Phenoxyacetic acid herbicides (see Chlorophenoxy herbicides) Phenoxybenzamine hydrochloride... 

The potential for environmental contamination continues to come from families of herbicides that have been used for years. The chlorophenoxy herbicides such as 2,4-D (2,4-dichlorophenoxy acetic acid) and 2,4,5-T (2,4,5-trichlorophenoxy-acetic acid) (Figure 5.1) are systemic acting compounds to control broadleaf plants and have been in use since the 1940s. The oral toxicities of these compounds are low. 

The widely used chlorophenoxy herbicides are chemical teratogens--as are their byproduct chlorodibenzodioxins. The symmetrical tetrachloro compound TCDD is perhaps the most toxic chemical known. 

In addition to the most popular chlorophenoxy herbicides, the group includes a variety of other chemical classes—e.g., amides, bipyridyls, carbamates, dinitrophenols, substituted ureas and triazines. Most of the chemicals tested are animal teratogens, as are many of the fungicides in this miscellaneous group (ref. 185. p. 578 and 586). 

IARC. 1986b. IARC mongraphs on the evaluation of carcingenic risks to humans. Occupational exposures to chlorophenoxy herbicides. Lyon, France World Health Organization, International Agency for Research on Cancer. IARC Monogr 41351-211. 

Kogevinas M, Saracci R, Winkelmann R, et al. 1993. Cancer incidence and mortality in women occupationally exposed to chlorophenoxy herbicides, chlorophenols, and dioxins. Cancer Causes and Control 4 547-553. 

Brillas, E., Boye, B., Sires, I., Garrido, J.A., Rodriguez, R.M., Arias, C., Cabot, P.-L. and Comninellis, Ch. (2004) Electrochemical destmction of chlorophenoxy herbicides by anodic oxidation and electro-Fenton using a boron-doped diamond electrode. Electrochim. Acta 49, 4487 1496. 

Kinetic analysis of all concentration decays tit well with the equation related to a pseudo-first-order reaction (see the inset panel of Fig. 19.11). The last column of Table 19.2 lists the k -values thus determined for the comparative treatments of chlorophenoxy herbicides. Similar k values can be observed for all electro-Fenton and photoelectro-Fenton treatments with Pt. This discards direct photolysis of herbicides by UVA light and significant participation of reaction (19.24) to generate OH. 

Our group has also investigated the influence of a BDD anode, with much higher oxidation power than Pt, on the anodic oxidation with electrogenerated H202 and electro-Fenton treatments of chlorophenoxy herbicides (Brillas et al. 2004b). Solutions with 100 mg dm-3 TOC of 4-CPA, MCPA, 2,4-D, and 2,4,5-T of pH 3.0 were... 

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