2,4,5-Trichlorophenoxy acetic acid (2,4,5-T) is a herbicide with the major use as a defoliant. Large amounts of the butyl esters of a 50:50 mixture of 2,4,5-T and 2,4-D (2,4-dichlorophenoxy acetic acid) – known as Agent Orange - were sprayed over Vietnam during the Vietnam War. Today, there are only a few production sites of 2,4,5-T. 2,4,5-T was found to be highly contaminated with 2,4,7,8-Cl4DD; no other PCDD or PCDF congeners have been identified. The highest concentration reported in a product from Germany was 7,000 ng I-TEQ/kg 2,4,5-T (present as 2,3,7,8-Cl4DD). 2,4,5-Trichlorophenol was mainly used as intermediate for the manufacture of 2,4,5-trichlorophenoxy acetic acid and hexachlorophene. A single measurement gave 680,000 ng I-TEQ/kg.
2,4,5-T is the most important derivative of 2,4,5-trichlorophenol (2,4,5-TCP). Commercially, 2,4,5-trichlorophenol is reacted with chloroacetic acid under alkaline conditions. Subsequent addition of sulfuric acid produces 2,4,5-T, which can then be reacted with a variety of alcohols or amines to produce 2,4,5-T esters and amine salts. Although, there have not been too many manufacturers of 2,4,5-T, there was a much higher number of companies marketing more than 400 formulated pesticide products containing 2,4,5-T (Esposito et al. 1980).
Hotspots in soil may exist at former 2,4,5-T production and handling sites.
The emission factor for commercial (technical product) 2,4,5-T is 7,000 μg TEQ/t product.
The emission factor for 2,4,6-trichlorophenol is 700 μg TEQ/t product.
The emission factor for dichlorprop is 1,000 μg TEQ/t product.
The emission factor for 2,4-D is 700 μg TEQ/t product (US-EPA 1998a, p 8-74). Concentrations may vary considerably: random samples from American brands gave 3 μg TEQ/t and Asian and Russian brands had around 200 μg TEQ/kg (US-EPA 1998a, p 8-77). The ultimate fate of PCDD/PCDF in these products will depend on their use and be controlled by local conditions.
2,3,5,6-Tetrachloro-2,5-cyclohexadiene-1,4-dione (p-chloranil) is the precursor for the production of dioxazine dyes (for cotton, leather, and synthetics) and other chemicals (e.g., seeds and fungicides). Synthesis of pigments is from reaction of chloranil (or other halogenated benzoquinones) with aromatic amines to diarylaminochloroquinones and oxidative cyclization in high-boiling solvents, such as o-dichlorobenzene, in the presence of acylchlorides or sulfuric acid. Depending on the production process, p-chloranil can contain high contamination with PCDD/PCDF.
Two production processes are known:
The old Hoechst AG process via chlorination of phenol (used until 1990 in Germany). Utilizing this old process, p-chloranil was contaminated in the range of several hundred μg I-TEQ/kg with PCDD/PCDF (mostly PCDF). The contamination of the ortho congener was much lower (around 60 μg I-TEQ/kg).
The process developed by Rhône-Poulenc Chimie and used today by e.g. Clariant (Germany) via chlorination (with HCl) of hydroquinone. This process results in much cleaner products (p-chloranil: ∼7 μg I-TEQ/kg); the same quality is obtained by Tokoyama Soda (Japan).
In the USA, chloranil has been used as a fungicide and seed-dressing agent between 1937 and 1977. After 1977, all uses of chloranil in agriculture were banned. In Europe, chloranil has not been used as a fungicide or as a seed protectant. In Africa, chloranil has been used as a fungicide and seed-dressing agent at least until 1984.
Of the approximately 400 t of chloranil produced per year until 1989, 300 t/a were processed to pigments and 100 t/a to dyestuffs (BUA 1992). In the last year of its production 1990, Hoechst AG produced 300 t/a. Until 1989, 150-200 t/a have been exported and approximately 50-100 t/a have been imported by the Hoechst AG from India. It is known that in India the same process has been applied for the production of chloranil until the mid of 1990. Further imports into Germany have been estimated to be around 50-100 t/a (BUA 1992). Since 1990, the only producer in Western Europe and probably the largest producer of chloranil worldwide is Rhône-Poulenc Chimie of France. Smaller production sites of chloranil have been found to exist in India, which may still use the traditional phenol process. No information could be obtained for productions in Eastern Europe and the Russian Federation. However, it is known that chloranil has been produced in the Russian Federation and has been imported into Russia as well. There is no domestic production of chloranil in the United States of America (BUA 1992).
PCDD/PCDF contamination in the final products made from chloranil, such as dyestuffs and pigments, finally will end in wastes of polymers/plastics, textiles and packaging materials (paper, tin cans, etc.) to be disposed of as municipal solid waste or re-entering recycling processes. In the case of paper recycling and textile dyeing, the PCDD/PCDF will be released into water or found in the sludge.
The most important dioxazine pigment is C.I. Pigment Violet 23 (of Hoechst AG), which is used for lacquers, polymers, and printing inks. A similar use is for C.I. Pigment Violet 37 (of Ciba Geigy AG).
The emission factor for p-chloranil manufactured via the old Hoechst Farben process is 400,000 μg TEQ/t product.
The emission factor for o-chloranil is 60,000 μg TEQ/t product.
Dyestuffs on chloranil basis of this old production pathway can have 1,200 μg TEQ/t product.
The emission factor using the hydroquinone process for the manufacture of p-chloranil is 100 μg TEQ/t product.
Dioxazine dyes and pigments using the old process had concentrations between 20,000 and 57,000 μg TEQ/t (for Blue 106) and between 1,000 and 19,000 μg TEQ/t (Violet 23) (Williams 1992). In the USA, concentrations in chloranil were between 263,000 μg TEQ/t and 3,065,000 μg TEQ/t. The Carbazole Violet (dye-pigment) had 211,000 μg TEQ/t.
Quantitative information on discharges of PCDD/PCDF into the environment cannot be given due to lack of reliable analytical data. Releases into the hydrosphere are to be expected from the downstream industries such as the production of dyestuffs, from textile dyeing with the liquor bath, and from paper recycling (BUA 1992). Utilizing the Hoechst process, generation of 20 m³ of wastewater per ton of product has been reported, however PCDD/PCDF concentrations in the wastewater have not been published. The synthesis of dioxazine pigments is done in closed systems, so that normally, no effluents are generated.
PCDD/PCDF contamination might be dissolved in the solvent, e.g., dichlorobenzene, and would be concentrated in the distillation residues. The fate of these solid residues should be notified (e.g. if landfilled or incinerated).
Further, active carbon used in the production of the dyestuffs may contain PCDD/PCDF (in Germany, disposal is by hazardous waste incineration in rotary kilns) (BUA 1992).