Mancozeb
Beyond Pesticides Rating: Toxic

Mancozeb (Dithane^TM, Fore^TM, Karamate^TM) is an ethylene bisdithiocarbamate fungicide. Mancozeb is a General Use Pesticide, meaning a pesticide applicators license is not required to purchase or use this pesticide.  

Acute Toxicity

Mancozeb has a relatively low acute toxicity (oral rat LD50 > 5000 mg/kg, dermal rabbit LD50 > 5000 mg/kg) and receives an U.S. Environmental Protection Agency (EPA) toxicity class IV (I  = most toxic, IV = least toxic) rating, with the word CAUTION appearing on all product labels. Despite its low acute toxicity, mancozeb is a skin and eye irritant. Workers exposed to the pesticide have developed rashes.  

Chronic Toxicity

Mancozeb is also a suspected endocrine disruptor, is mutagenic, and EPA classifies it as a class B2 probable carcinogen (PANNA, 2000). In chronic exposure studies, impaired thyroid function was observed as exposure to mancozeb lowered iodine uptake after 24 months in dogs fed doses of 2.5 and 25 mg/kg/day (ETN, 1996). In rat studies, pregnant females exposed to the pesticide had offspring affected by the exposure. 

Metabolites

A major toxicological concern in situations of chronic exposure is the generation of ETU, a metabolite of mancozeb. In addition to having the potential to cause goiter, a condition in which the thyroid gland is enlarged, this metabolite has produced birth defects and cancer in experimental animals (ETN, 1996). 

Ecological Effects.

Mancozeb is highly toxic to fish and other aquatic organisms, and slightly toxic to birds. 

Environmental Fate

In the field, mancozeb has a half-life in the soil of 1 to 7 days. However, ethylenethiourea (ETU), a toxicologically significant metabobilte (breakdown product) of mancozeb, may persist up to 10 weeks (ETN, 1996). 

Resources:

Extension Toxicology Network (ETN). 1996. “Mancozeb.” Pesticide Information Profiles. <http://ace.orst.edu/cgi-bin/mfs/01/pips/mancozeb.htm>. 

Pesticide Action Network North America (PANNA). 2000. “Mancozeb.” Chemical Information. <http://data.pesticideinfo.org/4DAction/GetRecord/PC35080>.