Iodomethane, also known as methyl iodide (CAS 74-88-4), has had a complex relationship with environmental and health regulations, largely due to its past use as a pesticide and its inherent toxicological profile. Approved by the U.S. Environmental Protection Agency (EPA) in 2007 as a pre-plant soil fumigant, it was intended to control a variety of agricultural threats, including insects, plant parasitic nematodes, soil-borne pathogens, and weed seeds. This application positioned Iodomethane as a potential alternative to methyl bromide, a substance phased out due to its ozone-depleting properties.

However, the registration and use of Iodomethane as a pesticide were met with significant controversy and scientific debate. Concerns were raised by various environmental and public health organizations regarding its toxicity. Studies indicated that Iodomethane is acutely toxic through inhalation, ingestion, and skin absorption, with potential effects on the central nervous system, lungs, and skin. More critically, it has been classified as a suspected human carcinogen, a designation that led to extensive reviews and legal challenges. The very properties that made it an effective fumigant—its volatility and potential to drift—also raised concerns about exposure risks for farmworkers and nearby communities, including vulnerable populations like children and fetuses.

These concerns culminated in the voluntary cancellation of its agricultural uses in the U.S. by the sole registrant, Arysta LifeScience, and the formal termination of its registrations by the EPA by the end of 2012. The decision was influenced by scientific reviews and public petitions highlighting potential unreasonable adverse effects on the environment and human health. While its use as a pesticide has largely ceased in many regions, Iodomethane continues to be used in laboratory settings and industrial processes where its properties are indispensable. Nonetheless, the history of Iodomethane as a pesticide serves as a potent case study in the ongoing challenge of balancing agricultural productivity with environmental stewardship and public health protection. The scientific community and regulatory bodies continue to monitor its applications and explore safer, more sustainable alternatives across all its uses, reflecting a broader shift towards greener chemistry and responsible chemical management.