Introduction:

Newborn attention

Organochlorines, including industrial chemicals such as polychlorinated biphenyls (PCBs) and p,p'-dichlorodiphenyl dichloroethene (p,p'-DDE), the major degradation product of the pesticide p,p'-dichlorodiphenyl trichloroethane (p,p'-DDT), though banned in the U.S. in the 1970s, are highly persistent in the environment and in human tissue. Previous literature suggests an association between prenatal organochlorine exposure and childhood behavior, including inattention (Grandjean et al. 2001; Jacobson and Jacobson 1996; Jacobson and Jacobson 2003; Vreugdenhil et al. 2004). Several studies report associations between PCBs and the Neonatal Behavioral Assessment Scale (NBAS) using summary clusters (Jacobson et al. 1984; Lonky et al. 1996; Rogan et al. 1986; Stewart et al. 2000). We investigated the association between low-level prenatal organochlorine exposure and attention in early infancy using individual NBAS items to characterize young infants' attention skills.

Methods:
An association between organochlorines and NBAS measures of attention was investigated in 788 infants born 1993-1998 to mothers residing near a PCB-contaminated harbor and Superfund site in New Bedford, Massachusetts. Cord blood samples for organochlorine analyses were collected at the infant's birth and analyzed for PCBs and DDE. Newborns were examined within a few days of birth and at approximately 2 weeks. Associations between organochlorines and NBAS measures of attention at 2 weeks were estimated using linear regression analysis, adjusting for a number of covariates.

Results:
For the 542 subjects with an NBAS exam at 2 weeks, we observed consistent inverse associations between cord serum PCBs (median and range=0.19, 0.01-4.41 ng/g serum), dioxin-like PCBs (median and range=4.41, 0-151.49 pg/g lipid), and DDE levels (median and range=0.30, 0-10.29 ng/g serum), and NBAS measures of alertness, quality of alert responsiveness, and cost of attention (Figure 1). Organochlorines were also associated with reduced self-quieting and motor maturity, and increased irritability and spontaneous activity. There was no observed association with previously studied summary cluster measures.

Discussion:
The approach to analyzing the NBAS in this study was different than previous studies of organochlorine exposure that used clusters to summarize NBAS outcomes. We hypothesized an association between PCBs and attention and therefore analyzed a priori selected individual NBAS items that we believe reflect attention-related skills. Our results show consistent inverse associations between organochlorine cord serum levels and attention-related NBAS outcomes. The association between organochlorines and increased spontaneous activity is consistent with hyperactivity-impulsivity observed in experimental animal models of early life PCB exposure. These observed associations are notable given the low levels of PCBs found in this population and limitations of behavioral assessments in young infants. Identifying possible attention-related deficits in infancy and potentially remediable risk factors for such deficits (for example, PCB exposure), allows for early intervention (and ultimately prevention efforts), which may be important for promoting healthy subsequent neurodevelopment.

Figure 1.
Associations and 95% confidence limits between cord serum levels of the sum of four PCB congeners (118, 138, 153, 180), dioxin-like PCBs and DDE, and 2-week NBAS measures of attention (alertness, quality of alert responsiveness, and cost of attention), adjusted for infant's age at exam, birth year, time since last feeding, NBAS examiner, and maternal age, education, marital status, parity, smoking during pregnancy, OB risk score and cord blood lead level for term infants born in New Bedford, 1993-1998.