NMU is an alkylating agent, and exhibits its toxicity by transferring its methyl group to nucleobases in nucleic acids, which can lead to AT:GC transition mutations.

[2][3] It has the potentially advantageous property that the stoichiometric byproducts formed are water, carbon dioxide, and ammonia, which are innocuous or easily removed.

However, because it is unstable at temperatures beyond 20 °C and somewhat shock-sensitive, it has become obsolete for this purpose and replaced by other N-nitroso compounds: (N-methyl)nitrosamides and nitrosamines.

[citation needed] Acute exposure to NMU in humans can result in skin and eye irritation, headache, nausea, and vomiting.

[5] However, the actual potential for human exposure is quite limited, as the chemical is not produced or used in large quantities [5] NMU is teratogenic and embryotoxic, resulting in craniofacial (cleft palate) and skeletal defects, fetal growth retardation, and increased fetal resorption.