Statistics on concentration of PCB 153 in cord blood serum C0 and at 6, 16 and 45 months of age (C6, C16 and C45, respectively) and duration of breast feeding tbf are shown in upper part of . The concentration data for all time intervals were positively skewed and lognormally distributed (one-sample Kolmogorov-Smirnov Test). The following weight increase in g in children of our cohort has been observed (means±SE): birth weight 3277.87±486.93, 6 months 7791.78±1098.81, 16 months 11802.13±1508.45 and 45 months 17241.94±2986.03.
Table 1 Descriptive statistics on duration of breast feeding tbf (months) and PCB 153 serum concentration (ng/g lipids) measured in cord blood serum and venous serum at 6, 16 and 45 months of age (C0, C6, C16 and C45, respectively) (upper part) and on computed (more ...)
The capability of the suggested model to describe the PCB 153 serum concentration in infants with various duration of breast feeding can be seen from . The model describes well the PCB 153 serum concentration and at the time of weaning the massive uptake of PCB 153 ceased which was reflected by the onset of serum PCB 153 decrease.
The measured PCB 153 serum concentrations and the calculated curve for six children with markedly different duration of breast feeding tbf. Note the markedly different vertical scales.
is showing PCB 153 measured serum concentrations and the calculated approximations for 12 infants with equal duration of breast feeding of 16 months and rank ordered according to the estimated MT. It can be seen that in the 2 children in which the concentration increased after weaning, the longest MTs, 108 and 134 months, were observed. The kinetics of PCB 153 serum concentration of each child was described by parameters MT, Cbf,∞ Cf,∞ and AUC ( lower part). The individual values of Cbf,∞ and Cf,∞ were normalized with regard to C0 in order to illustrate better the kinetics of PCB 153 in the body.
Model approximation of PCB 153 serum concentration values in 12 infants all breast fed 16 months and rank ordered according to increasing mean time (MT) in months.
Spearman's correlations in show that Cbf,∞ is related to AUC (: r=0.84, p<0.001) and that tbf predicts AUC (: r=0.86, p<0.001), Cbf, ∞ (: r=0.64, p<0.001), Cbf, ∞/C0 (: r=0.85, p<0.001), Cf, ∞ ( : r=0.78, p<0.001) and Cf, ∞/C0 (: r=0.78, p<0.001). MT was related to AUC (r=0.6, p<0.001), Cbf, ∞ (r=0.55, p<0.001), Cbf, ∞/C0 (r=0.71, p<0.001), Cf, ∞ (r=0.60, p<0.001) and Cf, ∞/C0 (r=0.59, p<0.001). The ratio Cbf, ∞/Cf, ∞ for 89 infants was >1, only for 4 infants the build up of PCB 153 body burden via normal food intake was greater than via milk. The model enables estimation of an AUC for each individual child. To demonstrate this, AUC values were calculated for increasing time for 4 children with largely varying duration of breast feeding ().
Figure 5 Spearman's correlations between the parameter values AUC vs. Cbf, ∞ and tbf vs. AUC, Cbf, ∞, Cbf, ∞/C0, Cf, ∞ and Cf, ∞ /C0 describing kinetics of PCB 153 serum concentration in 93 infants from birth to month 45 (more ...)
Figure 6 Time dependence of AUC in four children with different duration of breast feeding, tbf. For child ID=3934, 3084, 3877 and 4316 tbf was 24, 18, 7, 1 months and Cbf, inf/C0 was 11.92, 3.97, 14.4, 1.95, respectively. Note the markedly different vertical (more ...)