Prodiamine belongs to a group of human-made herbicides called dinitroanilines. Prodiamine is used in non-crop areas, nurseries, golf courses, and residential land.¹ It was first registered for use in 1992.² Prodiamine is used to control annual grasses and broadleaf weeds.^3,4 Prodiamine is a selective herbicide that can be used before planting or emergence.^4,5

There are over 500 pesticide products that contain prodiamine.⁶ Prodiamine is sometimes used in products with other herbicides. Some products with prodiamine might also contain fertilizers. Prodiamine is used as a dust, emulsifiable concentrate, soluble concentrate, water dispersible granule, dry flowable, flowable concentrate, granular, or ready-to-use product.^6,7

Prodiamine is not used in organic horticulture.⁸

Prodiamine interferes with cell division to stop root and shoot growth.⁹

When prodiamine enters the body, it is rapidly excreted. After 24 hours, rats eliminated around 70% of the total dose. Most of the prodiamine was detected in the feces. The amount found in tissue 4 days later was 0.5-1.4% of the initial dose.¹³

Researchers gave rats a single dose of either 10 mg/kg or 400 mg/kg prodiamine. They also fed the rats daily with 10 mg/kg prodiamine for 2 weeks. In all cases, the rats had eliminated the prodiamine within 4 days after feeding had stopped. Female rats had higher tissue levels of prodiamine. The residues were found throughout the body. Most of the dose was eliminated in the feces and urine.⁷

There are no studies available on dermal absorption, or how well prodiamine passes through the skin. However, the U.S. EPA used a related chemical to estimate dermal absorption. Based on that, they expect 3% would be absorbed by the skin into the body.⁷

The U.S. EPA classifies prodiamine as a "Group C - Possibly Carcinogenic to Humans" based on thyroid tumors in male and female rats.⁷ Prodiamine did not cause cancer in mice.^3,7,14 Prodiamine was negative for mutagenicity in all available studies. However, the U.S. EPA determined that it is plausible that two of the breakdown products of prodiamine are carcinogens and mutagens.⁷

The target organ of prodiamine in animals is the thyroid.⁷ This means the thyroid is the organ most likely to be harmed if an animal is exposed. Researchers have not identified a specific target organ in humans. However, prodiamine can affect the liver, thymus gland, and thyroid gland.¹⁵

When researchers fed rats prodiamine at 0, 400, 1200, or 4000 parts per million (ppm) for 13 weeks, the rats had effects at the highest dose of 4000 ppm in their food. At that dose, the rats gained less body weight, had increased cholesterol, and had increased urinary protein content.³ Rats eating 4000 ppm prodiamine for 13 weeks also ate less than rats in the other groups and their kidneys and livers were heavier. No effects were observed at 1200 ppm (80 mg/kg body weight) based on the effects seen at the highest dose of 4000 ppm.¹³

When beagle dogs ate prodiamine at either 0, 200, 600, or 2000 ppm for 13 weeks, dogs that were fed 600 ppm had changes in their blood. Dogs fed the highest dose of 2000 ppm had changes in their blood, heavier livers, liver damage, and their reproductive organs weighed less. Researchers did not see any changes in the dogs fed 200 ppm (5 mg/kg body weight).¹³

In another study, beagle dogs who ate 2000 ppm per day of prodiamine for 52 weeks had heavier livers and changes in blood chemistry compared to dogs that ate less or none.¹³

No human studies were found on the long-term effects of prodiamine.

Children are at an increased risk to pesticides due to their smaller body size, ongoing organ development, and different behaviors. Keep all pesticides out of reach of children and pets to avoid accidental ingestion.

Young children may act in ways that put them at greater risk of being exposed. For example, they may spend more time near the floor. They may also be more likely to place their hands in their mouths after touching treated surfaces or pets. The U.S. EPA concluded that prodiamine should not be more toxic to children than adults and no additional safety factors in the risk assessments were needed.¹⁶

Researchers found a birth defect called omphalocele after feeding pregnant rats 300 mg/kg of prodiamine. This is a defect where organs stick out through the abdominal wall. Pregnant rats and rabbits fed 1000 mg/kg and 300 mg/kg respectively gained less weight than unexposed pregnant rats and rabbits.³

Pesticides that enter the environment can affect wild plants and animals. Prodiamine has a potential to bioaccumulate in aquatic organisms.¹⁸

Birds

Birds might be exposed to prodiamine by eating granules, feeding on exposed prey, or by contact with a pesticide product containing prodiamine. Water containing trace amounts of prodiamine is not expected to be toxic to birds.¹⁸

• Short-term feeding studies have shown prodiamine is practically non-toxic to the canary.¹⁸
• Northern bobwhite quail and mallard ducks ate up to 1000 ppm prodiamine for 21 weeks. Researchers observed no harm to their health, survival, or reproductive development.¹³

Aquatic animals

Prodiamine is practically insoluble in water. This makes it difficult for researchers to accurately measure how much is in water when they run tests and look for impacts to aquatic organisms.¹³ However, the amount that can dissolve is low in toxicity to fish. Overall, scientists saw reproductive effects in freshwater fish and invertebrates exposed to prodiamine. However, none of the animals died during tests.¹⁸

• Researchers exposed bluegill sunfish to prodiamine concentrations of 18 to 320 mg/L for 96 hours. None of the fish died, but all showed signs of excitability at 96 hours.¹³
• Fathead minnows were exposed to prodiamine in their water for 16 weeks. On average, they had fewer eggs for each spawn and fewer eggs per female per day.¹⁸
• In a long-term study, scientists exposed rainbow trout to 25 μg/L prodiamine for an unknown period of time. The fish were shorter and weighed less compared to unexposed fish. The U.S. EPA concluded that the effects occurred near the limit of solubility of prodiamine in water.¹⁸
• Researchers exposed water fleas to various concentrations of prodiamine up to 100 mg/L for 48 hours. After 24 hours, the water fleas exposed to concentrations of 18 mg/L or more had erratic behavior.¹³

Bees

Prodiamine is low in toxicity to honeybees following contact and slightly toxic following ingestion.^13,18 More data may be needed to fully evaluate risks to pollinators, especially chronic exposure to bees.¹⁹

Worms and insects

Prodiamine is low to moderately toxic to earthworms.^13,20

• Scientists placed adult earthworms on discs of filter paper treated with prodiamine at five different concentrations for 48 hours. They determined that contact with the prodiamine paper was relatively non-toxic.²⁰
• The same scientists exposed 10 adult earthworms to soil containing various amounts of prodiamine. The soil exposure was moderately toxic to earthworms.²⁰
• Other scientists found that earthworms exposed to 1000 mg/kg of prodiamine in dry soil for two weeks lost weight.¹³

Prodiamine does not affect the development of other beneficial insects.¹³

• Researchers submerged aphids parasitized by wasps in levels of prodiamine that would be expected in the field. The young wasps were not affected.¹³
• The researchers also submerged ladybug larvae and green lacewing larvae in the prodiamine solution, and they also were not negatively affected.¹³

Soil microorganisms were not affected when scientists treated their soil with prodiamine for 28 days. The soil type was sandy loam.¹³