Objectives Identify erythrocytosis and neuropsychological alterations in highway workers exposed chronically to low concentrations of CO.

Method Cross-sectional study that included 72 workers of the Mexico-Puebla Highway cabins (guards); 60 cashiers and 12 workers in charge of the shift, in which socio- demographic, clinical and occupational variables were explored; haemoglobin (Hb), hematocrit (HCT) and carboxyhemoglobin (COHb) was determined in their blood, and it was applied the CONSB for CO. The workers who are in charge of the full shift integrated the less exposed to CO group, while the cashiers would shape the greater exposure group.

Results In 49 workers, Hb: 18.1 ± 1.9 mg/dL and Hcto: 55.3 ± 8.7 without significant differences in the presence or absence of erythrocytosis between exposure groups (p = 0.82). In the neuropsychological tests of 72 workers, greater alteration was identified in the exposed group, only in the test of symbol and digits (p = 0.001), trail making B (p = 0.002), and test of digits (p = 0.003); the test of building with blocks resulted borderline (p = 0.07). In all tests except in the test of learning of Rey, the non-exposed showed better performance.

Conclusions Despite what has been achieved, it is important to follow up the erythrocytosis and the neuropsychological effects on all workers, in addition to start treatment to prevent complications. The perception of innocuousness of chronic exposure to CO in these workersmust avoid.