The fact that (i) B[a]P is biotransformed for a part into 7,8-diol-B[a]P before becoming a reactive electrophile able to covalently bind DNA and/or to generate reactive oxygen species, (ii) 9-OH-B[a]P and 7,8-diol-B[a]P are detected in serum when behavioural impairments and changes in Nr1 and Nr2a/Nr2b subunit expression Nmda are observed, and (iii) there was a strong association between concentration levels of 9-OH-B[a]P and 7,8-diol-B[a]P in serum and those in brain, leads us to assume that both metabolites could be a suitable indicator of cognitive impairment triggered by B[a]P. The gene discussed is GRIN2B; the disease is Cognitive impairment.