Ziram

Health effects

Acute toxicity

If humans are exposed to ziram through inhalation for a prolonged period of time, they may develop nerve and irreversible eye damage. Ziram has also been observed to cause irritation of the skin, nose, and throat.

Chronic toxicity

Ziram ingestion has been proven to cause decreased antibody formation and diminished growth and development in rats. Rats also have been shown to develop various motor changes when administered ziram at unknown doses and duration. However, the definitive effects of ziram are still not well understood, as a one-year study has shown no effects on rats receiving a low dose of 5 mg/kg/day. Additionally, dogs that were administered ziram exhibited no harmful effects at this same duration and dose.

Reproductive effects

Ziram has deleterious effects on both the male and female reproductive systems in rats when administered at a moderate dose of 50 mg/kg. Female and male rats that ingested ziram at this dose two months before pregnancy exhibited reductions in fertility and litter size. Ziram has also been shown to inhibit fetal growth and organ development when pregnant mice ingested at both low and high doses.

Birth effects

Ziram can be mutagenic to humans who are chronically exposed to it in the air at moderate concentrations. The compound’s mutagenic effects include an increase in the number of chromosomal changes.

Cancer

A 103-week study has shown that ziram is correlated with thyroid cancer in rats, but no increase in cancer in female rats or male mice was seen. However, female rats did exhibit an increase in lung cancer. These findings are inconclusive, as the results were muddied by a viral infection, making the cause of cancer difficult to determine.

Parkinson's disease

Long-term exposure to pesticides, particularly ziram, is associated with Parkinson's disease. It appears to do this by directly damaging dopaminergic neurons. A recent study from UCLA suggests that blocking or removing α-synuclein might delay or prevent disease progression, based on research in zebra fish.

Legislation

Ziram has been determined to have moderate acute toxicity. It is rated as toxicity category II/III for oral and dermal exposure, category II for inhalation, category I for eye irritation, and category IV for skin irritation, with category I being the most toxic and category IV being the least.

Tolerances for the amount of ziram considered acceptable in food are first calculated as zinc ethylenebisdithiocarbamate, and then multiplied by a conversion factor of 0.6 to express the residue value in terms of carbon disulfide. Currently accepted tolerance for residues is 7 ppm for most uses. In 1986, the United States enacted the Emergency Planning and Community Right-to-Know Act and the Pollution Prevention Act, which required companies releasing toxic chemicals to report to the EPA when and how much of the chemical was being spread. Ziram is on this list of toxic chemicals.

Ziram is classified as "slightly hazardous" by the World Health Organization, which tests chemical toxicity by measuring rat oral LD_50, the dose (in milligrams of substance per kilogram of body weight) that kills 50% of the experimental rats.

Ziram was placed on the European Union Prioritization List to be further tested for endocrine-disrupting activity.

Persistence in the environment

While Ziram has not been found in groundwater, ziram is moderately detected in soils with medium to high content of organic matter. However, ziram only moderately persists in soils, as it has a field half-life of 30 days In water, ziram is the most stable of all metallic dithiocarbamate fungicides, which means degradation is rather slow. If ziram reaches the bottom of a body of water, it may stay there for months. However, in plants, ziram is readily broken down; carbon disulfide is released, as evidenced by the acidic surfaces (dissolved carbon dioxide).

Ecological effects

The three major ways ziram is depleted are: hydrolysis, photodegradation, and aerobic soil metabolism. The Environmental Protection Agency has concluded that ziram poses a low toxicity risk to mammals, a moderate risk to birds, and a high risk to aquatic species. After reviewing studies that investigated the effect of ziram on aquatic organisms, the Pesticide Action Network Pesticide Database concluded that its LC₅₀ dose (amount of pesticide that is lethal to 50% of the test organisms within the stated study time) for amphibians places it in the "highly toxic" category. Similarly, ziram has been found to be "highly toxic" for fish, "highly toxic" for zooplankton, and "moderately toxic" for molluscs.

History

Ziram started being used in the United States in 1960 as a broad-spectrum fungicide. It was used on a variety of crops to control many different fungal infections, including scab on apples and pears, leaf curl in peaches, and anthracnose and blight in tomatoes. In 1981, additional uses for ziram were approved, including the prevention of leaf blight and scab on almonds, shot-hole in apricots, brown rot and leaf spot in cherries, and scab and anthracnose in pecans. Ziram also began to be used on residential ornaments as a bird and mammal repellent.

Synthesis

The materials needed to begin the synthesis of ziram are zinc oxide and carbon disulfide. A liquid suspension with carbon disulfide, emulsifier, oil, and dissolved urea in water is formed. Zinc oxide and dimethyl amine are added to the solution. This suspension is agitated for a period of time to allow reactions to occur between the zinc oxide, carbon disulfide, and dimethyl amine. This leads to the production of ziram. This entire process takes place under 40°C.