title: Alterations in biochemical markers due to mercury (Hg) exposure and its influence on infant's neurodevelopment.
abstract: This study examined the role of oxidative stress due to mercury (Hg) exposure on infant's neurodevelopmental performance. A total of 944 healthy Saudi mothers and their respective infants (aged 3-12 months) were recruited from 57 Primary Health Care Centers in Riyadh City. Total mercury (Hg) was measured in mothers and infants urine and hair samples, as well as mother's blood and breast milk. Methylmercury (MeHg) was determined in the mothers and infants' hair and mother's blood. Urinary 8-hydroxy-2'-deoxyguanosine (8-OHdG), malondialdehyde (MDA), and porphyrins were used to assess oxidative stress. The infant's neurodevelopment was evaluated using Denver Developmental Screening Test II (DDST-II) and Parents' Evaluation of Developmental Status. The median total Hg levels in mother's urine, infant's urine, mother's hair, infant's hair, and mother's blood and breast milk were 0.995μg/l, 0.716μg/l, 0.118μg/g dw, 0.101μg/g dw, 0.635μg/l, and 0.884μg/l respectively. The median MeHg levels in mother's hair, infant's hair, and mother's blood were 0.132μg/g dw, 0.091μg/g dw, and 2.341μg/l respectively. A significant interrelationship between mothers and infants Hg measures in various matrices was noted. This suggests that mother's exposure to different forms of Hg (total and/or MeHg) from various sources contributed significantly to the metal body burden of their respective infants. Even though Hg exposure was low, it induced high oxidative stress in mothers and infants. The influence of multiplicative interaction terms between Hg measures and oxidative stress biomarkers was tested using multiple regression analysis. Significant interactions between the urinary Hg levels in mothers and infants and oxidative stress biomarkers (8-OHdG and MDA) were noted. The MeHg levels in mother-infant hair revealed similar interaction patterns. The p-values for both were below 0.001. These observations suggest that the exposure of our infants to Hg via mothers either during pregnancy and/or neonatal life, promoted oxidative stress that might have played a role in infant neurodevelopmental delays that we reported previously. The results confirmed that the interaction between infant's MeHg in hair and 8-OHdG and MDA levels was significantly associated with a delay in DDST-II performance (ß=-0.188, p=0.028). This finding provides an insight into the potential consequences of Hg-induced oxidative stress to infant's cognitive neurodevelopment for the first time. This observation still needs future studies to be validated. Given the low MeHg levels in our population, these findings are of particular importance.
authors.affiliation: Environmental Health Program, King Faisal Specialist Hospital and Research Centre, PO Box: 3354, Riyadh 11211, Saudi Arabia. Electronic address: iman@kfshrc.edu.sa.
authors.forename: Iman
authors.initials: I
authors.lastname: Al-Saleh
authors.affiliation: Environmental Health Program, King Faisal Specialist Hospital and Research Centre, PO Box: 3354, Riyadh 11211, Saudi Arabia.
authors.forename: Rola
authors.initials: R
authors.lastname: Elkhatib
authors.affiliation: Environmental Health Program, King Faisal Specialist Hospital and Research Centre, PO Box: 3354, Riyadh 11211, Saudi Arabia.
authors.forename: Reem
authors.initials: R
authors.lastname: Al-Rouqi
authors.affiliation: Environmental Health Program, King Faisal Specialist Hospital and Research Centre, PO Box: 3354, Riyadh 11211, Saudi Arabia.
authors.forename: Mai
authors.initials: M
authors.lastname: Abduljabbar
authors.affiliation: Environmental Health Program, King Faisal Specialist Hospital and Research Centre, PO Box: 3354, Riyadh 11211, Saudi Arabia.
authors.forename: Chafica
authors.initials: C
authors.lastname: Eltabache
authors.affiliation: Environmental Health Program, King Faisal Specialist Hospital and Research Centre, PO Box: 3354, Riyadh 11211, Saudi Arabia.
authors.forename: Tahreer
authors.initials: T
authors.lastname: Al-Rajudi
authors.affiliation: Department of Neurosciences, King Faisal Specialist Hospital and Research Centre, PO Box: 3354, Riyadh 11211, Saudi Arabia.
authors.forename: Michael
authors.initials: M
authors.lastname: Nester
mesh_terms: D000080242:8-Hydroxy-2'-Deoxyguanosine; D000328:Adult; D015415:Biomarkers / Q000032:analysis / Q000097:blood / Q000652:urine; D002657:Child Development; D003849:Deoxyguanosine / Q000031:analogs & derivatives / Q000652:urine; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000032:analysis* / Q000097:blood / Q000652:urine; D005260:Female; D006197:Hair / Q000737:chemistry; D006801:Humans; D007223:Infant; D008297:Male; D008315:Malondialdehyde / Q000652:urine; D018811:Maternal Exposure; D008628:Mercury / Q000032:analysis / Q000097:blood / Q000652:urine; D008767:Methylmercury Compounds / Q000032:analysis* / Q000097:blood; D008895:Milk, Human / Q000737:chemistry; D009035:Mothers; D009420:Nervous System / Q000254:growth & development*; D018384:Oxidative Stress; D011166:Porphyrins / Q000652:urine; D011247:Pregnancy; D012529:Saudi Arabia; D055815:Young Adult
chemical_list: D015415:Biomarkers; D004785:Environmental Pollutants; D008767:Methylmercury Compounds; D011166:Porphyrins; D008315:Malondialdehyde; D000080242:8-Hydroxy-2'-Deoxyguanosine; D008628:Mercury; D003849:Deoxyguanosine
keywords: Infants; Mercury; Mothers; Neurodevelopment; Oxidative stress; Porphyrins