Little is known about the mechanism by which ethylene glycol monomethyl ether (EGME) produces genotoxic effects in humans. The authors found that individuals exposed in utero to EGME showed characteristic dysmorphic features, unexplained mental retardation, and persistent cytogenetic damage. They hypothesized that these individuals had a higher level of terminal chromosome arrangements, accounting for the genomic instability detected. Results indicate that in utero-exposed individuals have significantly reduced telomeres relative to non-in utero-exposed participants. The M +/- SEM pixel intensity in the in utero-exposed participants was 43.6 +/- 7.6 compared with 74.1 +/- 1.9 in the non-in utero-exposed. Findings suggest that exposure to EGME in utero could result in terminal chromosome rearrangements and shortening of telomere length, leading to the observed dysmorphic features and idiopathic mental retardation.