Low-level prenatal lead exposure and infant sensory function.
Lead is a pervasive neurotoxicant that has been associated with poorer cognitive, behavioral, and motor outcomes in children. The effects of lead on sensory function have not been well characterized. The aim of this study was to assess the effects of prenatal lead exposure on infant sensory function, as measured by auditory brainstem response (ABR) and grating visual acuity (VA).



Lead was measured in maternal blood in mid- and late-pregnancy (mean gestational age = 15.5 and 39.0 weeks, respectively) and umbilical cord blood in a cohort of full-term infants in rural northeastern China. ABR latencies (peaks I, III, V) were measured in newborns during unsedated sleep (n = 315). The ABR central-to-peripheral (C-P) ratio was calculated as the ratio between the III-V and I-III interpeak intervals. VA was measured in 6-week-olds using Teller Acuity Cards (n = 1019) and assigned as the narrowest grid the infant fixated on. Multivariate linear regression was used to evaluate relationships between tertiles of mid-pregnancy, late-pregnancy, or cord lead and newborn ABR or 6-week VA.



Higher late-pregnancy lead levels were associated with higher ABR C-P ratios and lower VA. In covariate-adjusted analyses, mean C-P ratios were 4.6 and 3.2 % higher in infants whose mothers had lead > 3.8 μg/dL and lead = 2-3.8 μg/dL, respectively, than for infants whose mothers had lead < 2 μg/dL (p-trend =0.002). In adjusted analyses for VA, mean scores were 8.5 and 7.2 % lower for maternal lead > 3.8 μg/dL and lead = 2-3.8 μg/dL, respectively, compared to lead < 2 μg/dL (p-trend =0.009).



Auditory and visual systems maturation appears delayed in infants with higher prenatal lead exposure during late-pregnancy, even at relatively low levels. Both systems start myelinating in late gestation and mature rapidly in infancy. Higher ABR C-P ratio and lower grating VA scores suggest effects of low-level lead exposure on sensory system myelination.
Department of Environmental Health Sciences, University of Michigan, 1415 Washington Heights, Ann Arbor, MI, 48109, USA.
Monica K
MK
Silver
Department of Pediatric Ophthalmology, Peking University First Hospital, 8 Xishiku St., Xicheng, Beijing, 100034, China.
Xiaoqing
X
Li
Department of Otolaryngology, Peking University First Hospital, 8 Xishiku St., Xicheng, Beijing, 100034, China.
Yuhe
Y
Liu
Department of Pediatrics, Peking University First Hospital, 8 Xishiku St., Xicheng, Beijing, 100034, China.
Ming
M
Li
Center for Human Growth and Development, University of Michigan, 300 North Ingalls St., Ann Arbor, MI, 48104, USA.|Department of Psychology, Renmin University, 59 Zhongguancun St., Haidian, Beijing, 100872, China.
Xiaoqin
X
Mai
Center for Human Growth and Development, University of Michigan, 300 North Ingalls St., Ann Arbor, MI, 48104, USA.|Department of Biostatistics, University of Michigan, 1415 Washington Heights, Ann Arbor, MI, 48109, USA.
Niko
N
Kaciroti
Center for Human Growth and Development, University of Michigan, 300 North Ingalls St., Ann Arbor, MI, 48104, USA.|Department of Otorhinolaryngology, University of Michigan, 1500 E. Medical Center Dr., Ann Arbor, MI, 48109, USA.
Paul
P
Kileny
Center for Human Growth and Development, University of Michigan, 300 North Ingalls St., Ann Arbor, MI, 48104, USA.|Department of Psychology, University of Michigan, 530 Church St., Ann Arbor, MI, 48109, USA.
Twila
T
Tardif
Department of Environmental Health Sciences, University of Michigan, 1415 Washington Heights, Ann Arbor, MI, 48109, USA. meekerj@umich.edu.
John D
JD
Meeker
Center for Human Growth and Development, University of Michigan, 300 North Ingalls St., Ann Arbor, MI, 48104, USA.
Betsy
B
Lozoff
D004785:Environmental Pollutants / Q000097:blood*; D016057:Evoked Potentials, Auditory, Brain Stem; D005260:Female; D005312:Fetal Blood / Q000737:chemistry*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007854:Lead / Q000097:blood*; D008297:Male; D018811:Maternal Exposure; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D012677:Sensation; D014792:Visual Acuity
D004785:Environmental Pollutants; D007854:Lead
Auditory processing; Infants; Lead; Neonates; Visual acuity