Introduction

Vinclozolin (trade names: Ronilan, Curalan, Vorlan, Touche) is a common dicarboximide fungicide

Dicarboximide fungicides

Dicarboximide fungicides are a family of agricultural fungicides that include vinclozolin, iprodione and procymidone. Dicarboximides are believed to inhibit triglyceride biosynthesis in sclerotia-forming fungi, including Botrytis cinerea. These fungicides turn into 3,5-dichloroaniline in soil...

 used to control various diseases in vineyards, and on fruits and vegetables such as raspberries, lettuce, kiwi, beans and onions. It is also used on turf on golf courses. Two common fungi that vinclozolin is used to protect crops against are Botrytis cinerea

Botrytis cinerea

Botrytis cinerea is a necrotrophic fungus that affects many plant species, although its most notable hosts may be wine grapes. In viticulture, it is commonly known as botrytis bunch rot; in horticulture, it is usually called grey mould or gray mold.The fungus gives rise to two different kinds of...

 and Sclerotinia sclerotiorun  Fungicides like vinclozolin have played a role in crop maintenance in the United States. In the 1800s before the use of fungicides, areas of the United States saw crop losses up to 90 percent. With the arrival of synthetic fungicides in the mid 1900s came an increase in crop yield. Today, it is estimated that if left untreated, the yield for most fruit and vegetables would fall anywhere from 50 to 95 percent. In California alone, it has been estimated that the amount of grapes produced would drop 97 percent. Large amounts of vinclozolin are still used today, but its overall application has declined. As a pesticide, vinclozolin is regulated by the United States Environmental Protection Agency

United States Environmental Protection Agency

The U.S. Environmental Protection Agency is an agency of the federal government of the United States charged with protecting human health and the environment, by writing and enforcing regulations based on laws passed by Congress...

 (EPA). It has gone through a series of tests and regulations in order to outline the risks and hazards to the environment and animals. Among the research, a main finding is that vinclozolin has been shown to be an endocrine disruptor

Endocrine disruptor

Endocrine disruptors are chemicals that interfere with endocrine in animals, including humans. These disruptions can cause cancerous tumors, birth defects, and other developmental disorders...

, specifically, it is know to have antiandrogenic effects.

Use in the United States

Vinclozolin is manufactured by the chemical company BASF

BASF

BASF SE is the largest chemical company in the world and is headquartered in Germany. BASF originally stood for Badische Anilin- und Soda-Fabrik . Today, the four letters are a registered trademark and the company is listed on the Frankfurt Stock Exchange, London Stock Exchange, and Zurich Stock...

 and has been registered for use in the United States since 1981.The following is a compilation of data indicating the national use of vinclozolin per crop (lbs AI/yr) in 1987: apricots, 124; cherries, 3,301; green beans, 13,437; lettuce, 24,779; nectarines, 1,449; onions, 829; peaches, 15,203; plums, 163; raspberries, 3,247; and strawberries, 41,006. In 1997, two applications totaling 285 pounds each, were applied to kiwifruit in California to prevent the gray mold and soft rot cause by Botrytis cinerea. In general, the United States has seen an overall decline in the national use of vinclozolin. In 1992, a total of approximately 135,000 pounds were used. However, in 1997 this number dropped to 122,000 and in 2002 it was down to 55,000 pounds.

Preparation and Application

The following chemical reactions are used to make vinclozolin:

• Methyl vinyl ketone + sodium cyanide + 3,5-dichloroaniline + phosgene (cyanohydrin formation/nitrile hydrolysis/amide formation/phosgenation).
• Vinclozolin is also prepared by the reaction of 3,5-dichlorophenyl isocyanate with an alkyl ester of 2-hydroxy-2-vinylpropionic acid; ring closure is achieved at elevated temperature.

Vinclozolin is then formulated into a dry flowable or extruded granular. It can be applied by through the air (aerial), through irrigation systems (chemigation), or by ground equipment. Vinclozolin is also applied to some plants, such as decorative flowers, as a dip treatment where the plant is dipped into the fungicide solution and then dried. It is also common to spray a vinclozolin solution using thermal foggers in greenhouses.

History of Regulations

All pesticides sold or distributed in the United States must be registered by EPA. To qualify for registration, scientific studies need to show that the pesticide can be used without putting people or the environment at risk. The law also requires that pesticides which were first registered before November 1, 1984, be reregistered so that they can be retested using the now more advanced scientific methods. Because vinclozolin was released in 1981, it has gone through a preliminary registration, and also a subsequent reregistration.
Below is a list of the history of regulations for vinclozolin:

• A Data Call-In (DCI), requiring data on product and residue chemistry, toxicity, environmental fate, and ecological effects, have been requested in 1991, 1995 and 1996.
• Agricultural Data Call-In (AGDCI), to estimate what happens to workers after they apply the fungicide, was issued in 1995.
• In April 1997, BASF proposed a new use for vinclozolin and thus all risks were reevaluated under the Food Quality Protection Act (FQPA).
• In June 1998 the EPA put a new safety factor on vinclozolin. BASF voluntarily cancelled vinclozolin use on some fruits and turf.
• On July 18 2000 the EPA established that certain meat, bean and dairy products have a 3 year time-limited tolerances for vinclozolin and its metabolites. This lead to a phase-out of most domestic food uses for vinclozolin. In September 2000, the EPA received objections to the issued tolerance for beans.
• Other measures that BASF has taken to to reduce risks: cancel use on decorative plants and set up new restrictions on turf which state that the application to turf restricted to golf courses and industrial sites.

Safety

There are certain precautions that workers are advised to use while handling vinclozolin. Mixers and loaders must wear clothing that completely covers the skin. They must also wear a chemical resistant apron and gloves, along with protective eyewear. Those who use the air blast equipment must be in a closed cab that meets the definition in the Worker Protection Standard for Agricultural Pesticides for dermal protection.

Means of Exposure

The EPA has examined whether people can be exposed to vinclozolin by means of dietary (food and water), non-dietary and occupational exposure. In general, fungicides have been shown to circulate through the water and air, and it possible for them to end up on untreated foods after application. Consumers alone cannot easily reduce their exposure because fungicides are not removed from produce that is washed with tap water. It has been determined that people may be exposed to residues of vinclozolin and its metabolites containing the 3,5-dichloroaniline moiety (3,5-DCA) through diet, and thus tolerances limits have been established for each crop.. Although vinclozolin is not registered for use by homeowners, it is still possible for people to come in to contact with the fungicide and its residues. For example, golfers playing on treated golf courses, and families playing on sod which has been previously treated may be at risk for exposure. Occupationally, workers can be exposed to vinclozolin while doing activities such as loading and mixing.

Antiandrogen

As part of the reregistration process, the EPA reviewed all toxicity studies on vinclozolin. The main effect induced by vinclozolin is related to its Antiandrogen

Antiandrogen

Antiandrogens, or androgen antagonists, first discovered in the 1960s, prevent androgens from expressing their biological effects on responsive tissues. Antiandrogens alter the androgen pathway by blocking the appropriate receptors, competing for binding sites on the cell's surface, or affecting...

 activity and its ability to act as a Competitive antagonist

Competitive antagonist

A competitive antagonist is a receptor antagonist that binds to a receptor but does not activate the receptor. The antagonist will compete with available agonist for receptor binding sites on the same receptor...

 at the androgen receptor. Vinclozolin can mimic male hormones, like testosterone, and bind to androgen receptors, while not necessarily activating those receptors properly. There is evidence that vinclozolin itself binds weakly to the androgen receptor but that at least two of its metabolites are responsible for much of the antiandrogenic activity. In the rat model, it has been shown that the antiandorgenic effects of vinclozolin are most prominent during the developmental stages. In utero, this sensitive period of fetal development occurs between gestation days 16-17. When male rats were given low dose levels (>3 mg/kg/day) of vinclozolin, effects such as decreased prostate weight, weight reduction in sex organs, nipple development, and decreased ano-genital distance were noted. At higher dose levels, male sex organ weight decreased further, and sex organ malformations were seen, such as reduced penis size, the appearance of vaginal pouches and Hypospadias

Hypospadias

Hypospadias is a birth defect of the urethra in the male that involves an abnormally placed urinary meatus...

. In another animal model, birds, vinclozolin and its metabolites were shown in vitro and in vivo to inhibit androgen receptor binding and gene expression. Vinclozolin caused reduced egg laying, reduced fertility rate, and a reduction in successful hatches. Androgen also play a role in puberty, and it has been shown an antiandrogen like vinclozolin can delay pubertal maturation. Antiandrogenic toxins are also known to alter sexual differentiation and reproduction in the rabbit model. Male rabbits exposed to vinclozolin in utero or during infancy did not show a sexual interest in females or did not ejaculate.

Progesterone and Estrogen effects

Besides androgens, vinclozolin has been shown to effect other steroid hormone receptors, such as those of Progesterone

Progesterone

Progesterone also known as P4 is a C-21 steroid hormone involved in the female menstrual cycle, pregnancy and embryogenesis of humans and other species...

 and Estrogen

Estrogen

Estrogens , oestrogens , or œstrogens, are a group of compounds named for their importance in the estrous cycle of humans and other animals. They are the primary female sex hormones. Natural estrogens are steroid hormones, while some synthetic ones are non-steroidal...

. Just as with androgens, the timing of the exposure to vinclozolin determines the magnitude of the effects related to these hormones. In a study with rats, in vitro research showed the the ability of two vinclozolin metabolites to bind to the progesterone receptor. However, the same study in vivo using adult male rats showed no effects. When mice experienced vinclozolin exposure in utero, male offspring exhibited up-regulated estrogen receptor and up-regulated progesterone receptor. In females, vinclozolin down-regulated expression of estrogen receptors and up-regulated progesterone receptor expression. This result causes Virilization

Virilization

In biology and medicine, virilization refers to the biological development of sex differences, changes that make a male body different from a female body. Most of the changes of virilization are produced by androgens...

 and the feminization of males and masculinization of females.

Transgenerational Effects

Vinclozolin has been proven to result in trangenerational effects, meaning that not only is the initial animal affected, but effects are also seen in subsequent generations. One study demonstrated that vinclozolin impaired male fertility not only in the first generation that was exposed in utero, but in males born for three generations and beyond. Furthermore, when affected males with were mated with normal females, some of the offspring were sterile and some had reduced fertility. After three generations, male offspring continued to show low sperm count, prostate disease and high rates of testicular cell apoptosis.,

Links to Cancer

The EPA has classified vinclozolin as a possible human carcinogen. Vinclozolin induces an increase in Leydig cell

Leydig cell

Leydig cells, also known as interstitial cells of Leydig, are found adjacent to the seminiferous tubules in the testicle. They produce testosterone in the presence of luteinizing hormone...

tumors in rats. The 3,5-DCA metabolite is thought to posses a mode of tumor induction based on its similarity to p-choroaniline.

Environment

Laboratory test indicate that vinclozolin is easily broken down and dissipates in the environment with the help of microbes, soil metabolism, and transport with water. Vinclozolin has several metabolites that are the products of its degradation: Metabolite B, 3,5-DCA and metabolite E. Only 3,5 DCA appears to resist further degradation. In terrestrial field dissipation studies conducted in various states, vinclozolin dissipated with a half-life between 34 to 94 days. Half-lives including residues can reach up to 1,000 days. Residues may accumulate and be available for future crop uptake.

External links

• BBC article on Vinclozolin in rats