Applicability of the TDI concept to residues in human milk

The ADI/TDI approach implies chronic intake for the whole lifespan, which of course, does not apply to the breastfeeding period. In fact, breastfeeding for 6 months does account for less than 1% of the mean lifespan. Therefore, ADI/TDI values cannot be considered an appropriate instrument to adequately evaluate any health risk for infants' development in the context of breastfeeding. However, if daily substance intakes via breastfeeding are calculated to range below or within the ADI/TDI, it can be anticipated that any health risk is highly improbable.

This is illustrated in Table 2, which presents data on the current level of contamination with organochlorine pesticides in human milk samples from the Federal Republic of Germany. The milk analyses have been performed by the Federal Untersuchungsamter, which kindly provide their data to an inventory on residues in human milk at the Federal Institute for Health Protection of Consumers and Veterinary Medicine. Under quantitative aspects hexachlorobenzene (HCB), beta-hexachlorocyclohexane (P-HCH) and DDT still are relevant contaminants, whereas the other OCPs range near or at the level of determination. From the analytical data of OCP residues, the respective daily intakes can be estimated (assumptions for calculation: mean milk fat content 3.5%; mean milk fat intake 4.2 g/kg based on daily milk intake of 120 ml/kg body weight). Considering the estimates for the 95. percentile (P-95, the intake values for most of the indicated OCPs range at or below the TDI (exception HCB), some of them are even lower than the level of the NOAEL. It may be concluded therefore, that from the current levels of these OCPs no significant risk for adverse health effects can be expected and that these contaminants are ofno real concern for the health of the breastfed infants.

Table 2. Estimated daily intake ofpesticides and pesticide residues

(Hg/kg/d)

levelsin human milk**' mean 95-P (mg/kg milk fat)

estimated daily intake mean 95-P (|a.g/kg body weight)

HCB

0.06

0.16-0.17

0.07

0.18

0.29

0.76

alpha-HCH

0.5

3

0.003

0.01

0.01

0.04

beta-HCH

0.1

3

0.04

0.12

0.17

0.48

gamma-HCH

1.0

3

0.006

0.02

0.03

0.08

HE

0.05

0.5

0.008

0.02

0.03

0.08

Dieldrin

0.01

0.1

0.007

0.03

0.03

0.12

DDT

0.5

20

0.31

0.90

1.32

The situation is different however, for PCBs and dioxins. Although continuously decreasing with time, levels of PCBs are still detectable in significant amounts in human milk from Germany (Table 3). For PCBs the estimated daily intakes (mean and P-95 level) amount to 2 and 4 |g/kg body weight, respectively. This is compared to a provisional TDI of 1 |g/kg body weight/day. An appropriate TDI for PCBs still remains to be established. The problem is, that the composition of PCB residues in human tissues differs in congener pattern and amount from the composition ofthe technical products, which have been used in animal testing so far. The testing of relevant mixtures is still an outstanding issue.

Mean levels of dioxins in human milk, given as toxic equivalents (TEq) based on international toxic equivalency factors (I-TEF), are also decreasing. However, calculations based on the current residue levels in human milk samples from Germany clearly demonstrate, that the daily intake of babies by far exceeds the TDI of 1-10 pg I-TEq/kg body weight, which had been recommended by the former German Federal Health Office 5. At present, it is difficult to precisely figure out this excess intake during the period of breastfeeding. WHO, after reevaluation ofthe current data base has set the TDI at 1-4 pg WHO-TEq/kg body weight 6. In their new concept dioxinlike PCBs are considered besides dioxins/furans and contribute to the toxic equivalents. Hence, if dioxin-like PCBs are additionally taken into consideration, the current levels of dioxinlike compounds (PCDD/F + PCB) in human milk nominally may increase two to three fold.

Table 3. Estimated daily intake ofPCBs and dioxins

H. Przyrembel etal.

levels in human milk**)

estimated daily intake

PCBs

(mg/kg milk fat)

(|g/kg body weight)

(1 ^g/kgbw/d)

mean P-95

mean P-95

1997

0.50 0.94

2.1 3.9

Dioxins/Furans

(ng I-TEq/kg milk fat)

(pg I-TEq/kg body weight)

(1 -10 pg I-TEq/kg bw/d)

(l -4 pg WHO-TEq*))/kg bw/d)

mean

mean

1993

16.6

69.7

52.1 (~125pg(WHO-TEq*))

1997

12.4

*) 6, including dioxin-like PCBs

**) data from Germany

WHO well recognises the particular concern evolving from their new concept of evaluating dioxinlike chemicals with respect to the occurrence of such contaminants in human milk and therefore payed special attention to the issue ofbreastfeeding in their Executive Summary 6:

"Breast-fed infants are exposed to higher intakes ofthese compounds on a body weight basis, although for a small proportion of their lifespan. However, the consultation noted that in studies ofinfants, breast feeding was associated with beneficial effects, in spite of the contaminants present. The subtle effects noted in the studies were found to be associated with transplacental, rather than lactational exposure. The consultation therefore reiterated conclusions ofprevious WHO meetings on the health significance ofcontamination ofbreast milk with dioxin-like compounds, namely that the current evidence does not support an alteration of WHO recommendations which promote and supportbreast feeding."

New Mothers Guide to Breast Feeding

New Mothers Guide to Breast Feeding

For many years, scientists have been playing out the ingredients that make breast milk the perfect food for babies. They've discovered to day over 200 close compounds to fight infection, help the immune system mature, aid in digestion, and support brain growth - nature made properties that science simply cannot copy. The important long term benefits of breast feeding include reduced risk of asthma, allergies, obesity, and some forms of childhood cancer. The more that scientists continue to learn, the better breast milk looks.

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