To establish differences in the genotoxic effect of particulate matter (PM10) in exposed individuals at two sites in the Valle de Aburrá (VA). This was a descriptive cross-sectional study of 2 groups of individuals exposed to 67.7 and 45 µg/m3 of PM10 for a minimum of 8 hours/day. The frequency of Chromosomal Abnormalities (CAs) and the mitotic index were evaluated based on blood samples. The data were processed using SPSS version 18.0 and significant differences were established between the groups at p<0.05. One hundred eighteen individuals were evaluated: 56.8% at site 1 and 43.2% at site 2. The study population had an average age of 53 years. Significant differences were found between the numbers of CAs (p = 0.003) detected at the sample sites. Site 1 displayed a higher number of CAs than site 2, likely because site 1 is located in an area of the VA that is more exposed to environmental contamination. Furthermore, this study showed that there is a relationship between the level of particulate matter and an increase in a biomarker for CAs, establishing a possible health risk in this population, especially for those who remain there for long periods of time.