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MCPA(Chiptox,Dow MCP)Herbicide Profile 9/89 Page 2 of 6 3. -4W*nce Findings .4of This review of MCPA acid, its salts, and esters, is the second intensive evaluation of the compound. In its original Registration Standard, issued in 1982, the Agency summarized the available data `r supporting the registration of MCPA and concluded that additional data were needed to fully evaluate the pesticide. The Agency has since received and reviewed the data on these compounds. The Agency has registered 9 salts, esters and amines of MCPA in addition to the acid. From a toxicological standpoint the acid and the sodium salt are essentially identical. The registrants, however, must show that the other derivatives would be equivalent to MCPA acid under testing conditions. Otherwise, a complete set of data must be submitted on each derivative to support their continued registration. The following scientific assessment discusses the Agency's knowledge on MCPA acid. If the data refers to a derivative, the derivative is identified. Chemical/Physical Characteristics of the Technical Material MCPA is white to light brown and can be a solid, flakes, crystal powder or liquid. It has no odor or can be slightly phenolic smelling. The melting point is 114 to 119 degrees C and is soluble to varying degrees in various solvents. Toxicology Characteristics - Acute Oral. Toxicity Category III (LD50 1.38 g/kg in male rats, 0.76 g/kg in female rats) . - Acute Dermal. Toxicity Category III (LD50 > 4000 mg/kg in the rat) . - Acute Inhalation. Toxicity Category III (LC50 > 6.36 mg/L in the rat) . - Primary Eye Irritation. Toxicity Category I (corneal opacity with irritation of conjunctive observed 21 days post-instillation with rabbits) . - Skin Sensitization. Not a skin sensitizer in guinea pigs. Testing on other species required. - Acute Delayed Neurotoxicity. MCPA is not an organophosphate, therefore a study is not required. - Subchronic Oral. Sufficient data are available to satisfy the requirements of a subchronic oral study in rodents and nonrodents. In beagles there was evidence of dose-related liver and kidney toxicity. .� A NOEL for systemic effects was set at 1 mg/kg/day. In rats, the mid- and high-dose males exhibited increased kidney weights and both sexes had indications of kidney disfunction. Hepatotoxicity, based on prolongation of clotting times and decreased cholesterol concentrations occurred in high dose males. The NOEL for systemic effects is set at 2.5 mg/kg/day. - Subchronic Dermal. Data gap. A 21-day dermal toxicity study is rcrni rcri +� - Chronic Toxicity. Sufficient data are available to satisfy the requirements for the chronic feeding studies in two species for technical MCPA acid. In beagles, after one year, kidney and liver toxicity was observed at the mid- and high dose levels. The systemic NOEL was set at 0.15 mg/kg/day, LDT. - In a 2 year rat study, hepatotoxicity was observed with elevated triglycerides, decreased cholesterol, and kidney nephropathy. The NOEL for systemic toxicity was set 1.0 mg/kg/day. - Oncogenicity. Rat and mouse studies were reviewed and found acceptable. MCPA is considered to be non-oncogenic. No additional studies are required. - Teratogenic. The studies available to the Agency are unacceptable under current guideline requirements. While these studies showed no developmental alterations, the Agency is requiring teratology studies in two species. - Reproduction. In a two-generation reproduction study with rats, there were indications of a potential postnatal growth effect. The NOEL is set at 7.5 mg/kg/day. No additional reproduction studies are required. - Mutagenicity. The Agency has data to satisfy the Structural Chromosomal Aberration study and the DNA Damage and Repair study. r. MCPA acid was found to be non- mutagenic in the first study and weakly mutagenic in the second. The Agency is requiring a gene mutation http://pmep.cce.comell.edu/profiles/herb-growthreg/fatty-alcohol-monuron/mcpa/herb-prof-mcpa.html 10/30/2003