Dear Mary, I found a ref. in my files which might be useful to you. Wolff,M.: Occupationally Dreived Chemicals in Breast Milk. Am J Industr Med, 1983, 4:259-281. It contains a general section on solvents, which is, I guess, the main issue with your mom who is returning to work. Here is a brief excerpt: " The pharmacokinetic behavior of solvents is similar to that of inhalation anesthetics. Hydrocarbons and halogenated hydrocarbons are absorbed, mainly through the respiratory route, with almost infinite uptake possible by adipose tissue. Upon cessation of exposure, excretion occurs (1) directly via the lungs and (2) by metabolites in urine. Depending on volatility, respiratory excretion is usually complete within 8-24 hrs, although traces may remain in adipose tissue. However, compounds that are not readily metabolized remain in the body in spite of their volatility. For example, tetrachloroethylene (PCE) is detectable in breath as long as 2 weeks following exposure. This commonly used cleaning solvent was the source of a reported family exposure, where severe neonatal juandice was attributed to ingestion of PCE in breast milk. The father, who worked in a drycleaning plant, had 30ug/mg (pmm) PCE in blood. Two hours after visiting him at work, the mother had 3 ug/ml in blood. Her milk had 10 and 3 ppm PCE i and 24 hours after exposure. The infant recovered when breastfeeding was discontinued." What this says to me is that breathing solvents can be a problem, but I still don't know the answer to the specific solvents you are asking about. I saw acetane in a table in another study as a substance which had been detected in mother's milk, but it didn't say what the effect on the infant would be. Can she wear a breathing hood? Hope this is somehow helpful. Barbara Wilson-Clay, BSE, IBCLC