Propylene glycol monomethyl ether. A three-generation study of isomer β effects on reproductive and developmental parameters in rats

Propylene glycol monomethyl ether (PGME) is widely used as a solvent in numerous commercial products. Its chemical synthesis leads to the formation of two isomers: a and b, the latter being usually present in the range of 0.5-1.5%. Isomer α has been shown to be of low toxicity. Isomer β raises concerns as to its reproductive and developmental effects. We evaluated the reproductive and developmental toxicity of two different commercial mixes of PGME (Mix A: 99% isomer α and 0.5% isomer β, Mix B: 98.5% isomer α and 1.5% isomer β) on Sprague-Dawley rats. The use of two mixes allowed us to differentiate between isomer α and isomer β effects. Male and female rats were exposed through drinking water to mixes A or B during a gametogenesis cycle (64 days for males and 15 days for females) to 0, 2, 5, 10 and 15% (v/v) of each mix. These animals (F₀) and the three following generations (F₁, F₂ and F₃) were followed. We observed a statistically significant decrease in the number of pups in isomer α-treated animals of generation F₁ and a nondose-related variation of the sex ratio in F₁ and F₂ generations after PGME mix B treatment. The most important effect observed was a decrease in testicular and epididymal sperm counts in relation to PGME isomer β in acute daily exposure, on the first parental generation. The effect evidenced on sex ratio needs further work in order to assay the potential persistent effects of PGME exposure.