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Fact sheet

Breast milk and environmental pollutants in Norway - fact sheet

Published Updated

Amming
Foto: Colourbox.com

The amount of environmental pollutants in breast milk has decreased significantly in recent years.


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Environmental pollutants are harmful compounds that accumulate in the food chain and in the human body.

They can be divided into several subgroups. Here we will look at compounds that contain chlorine or bromine (halogenated pollutants) i.e.: 

  • dioxins / furans 
  • polychlorinated biphenyls (PCBs) 
  • a group of brominated flame retardants (polybrominated diphenyl ethers - PBDE) 
  • pesticides such as hexachlorobenzene (HCB), hexachlorocyclohexane (HCH) and dichlorodiphenyltrichloroethane (DDT).
  • Breastmilk - measurement of compounds

Where do pollutants come from?

Dioxins / furans are formed in industrial processes and combustion where chlorine and carbon are present. HCB can also be formed during combustion and industrial processes. The other compounds are chemicals which are synthesized for different uses.

Regulation

Substances are regulated by the Stockholm Convention on persistent organic pollutants. Production and use is banned in most countries, and emission to the environment is now reduced. Due to the long decay time, the compounds will remain in the environment and in humans for a long time.

How are we exposed to the pollutants?

In Norway, we are exposed to organic pollutants mainly through food, especially fatty fish and other seafood, but also from meat and dairy products. In other countries, other food sources or forms of exposure are important. The chemicals break down very slowly and are stored in body fat, but can be excreted in breast milk.

All the substances mentioned above are included in the World Health Organization’s breast milk monitoring programme. Norway has participated in this programme since it began in 1985. The Norwegian Institute of Public Health in cooperation with the Norwegian School of Veterinary Science has been involved in the implementation of the studies. Breast milk was collected in 1986, 1993, 2001 and 2005. Breast milk from 10 to 50 first-time birth mothers were mixed together and analyzed as one sample to get an average measure for each year. In addition, 450 individual samples were analyzed in 2003-2005 to see how the levels vary from woman to woman.

Studies of human milk can provide two types of information: 

  • they give us an idea of how much pollution people have been exposed to over time, and what changes have occurred
  • they give us an idea of what the foetus and breastfed children are exposed to.

Results of the measurements in Norway are presented below.

Dioxins / furans and dioxin-like PCBs in breast milk

From 1986 to 2005 the levels of dioxins and dioxin-like PCBs (dl-PCBs) decreased in breast milk by almost 70 per cent, see figure 1.

The decrease is due to extensive measures to combat emissions and dispersion of dioxins in the environment in European countries. Changes in chemical use, rules for waste incineration and the closure of polluting industries has probably also played a role.

The amount of dioxins and dl-PCBs in food and breast milk is calculated in toxic equivalents (TEQ).

 
 
Morsmelk dioksiner og dl-PCB NY 2010.gif
Figure 1. Dioxins and dioxin-like PCBs in human milk 1986-2005. Source : NIPH, Division of Environmental Medicine.

Pesticides, PCBs and brominated flame retardants in breast milk

The concentration of other PCBs (Figure 2) and pesticides DDT, HCH and HCB (Figure 3) has declined by 70 to 90 percent since measurements began in 1986.

 
 
Innhold av 6 PCBer.
Figure 2. Concentration of PCBs (sum of 6 PCBs) in human milk 1986-2005. Source: NIPH, Division of Environmental Medicine.
 
 
Morsmelk innhold DDT - ny fig 2010.gif
 
Morsmelk innhold HCH - ny fig 2010.gif
 
Morsmelk innhold HCB - ny fig 2010.gif
Figure 3. Concentration of pesticides DDT, HCH and HCB in human milk 1986-2005. Source: NIPH, Division of Environmental Medicine.

For brominated flame retardants (PBDEs, Figure 4) concentration increased in breast milk up to around 2000. Now the concentration seems to have stabilised or even to be decreasing. Similar trends have been observed in other European countries.

 
 
Morsmelk innhold PBDE - ny fig 2010.gif
Figure 4. Concentration of brominated flame retardants (sum of 7 PBDEs) in human milk 1986-2005. Source: NIPH, Division of Environmental Medicine.

Breast milk measurements indicate that the action taken in industry and government to reduce the emission of these environmental pollutants has resulted in less exposure to these pollutants. This will decrease the concentration in breast milk. Changes in food production and changes in dietary habits may also have contributed to the decline in levels.

Large variation

In table 1, variations from the lowest to the highest value found in the individual breast milk samples from 2003-2005 can be seen. Variations are large and indicate that women’s diet and storage of pollutants in fatty tissue varies between individuals.

Table 1 Variation in the concentration of various pollutants from a large survey of Norwegian human milk (HUMIS) in 2003-2005. Sum 6 PCBs stands for the sum of six PCBs. PBDEs are brominated flame retardants. HCB, HCH and DDT are pesticides.

Compounds

Average

Median

Lowest value

Highest value

pg TE per g milk fat:

Dioxins og DL-PCBs

11

-

4.6

18

nanogram per g milk fat:

Total 6 PCBs

83

73

10

454

Total 7 PBDEs

3.4

2.1

0.48

82

HCB

12

11

3.6

42

Total HCH

7.5

5.5

1.0

260

Total DDT

66

45

2.0

1300

The greatest difference between the lowest and highest measurement is found for the pesticides DDT and HCH.

The concentration of total DDT ranged from 2 to 1300 nanograms per gram of milk fat (ng / g). The highest value was therefore 650 times greater than the lowest, but half of the mothers had concentrations in milk under the median value of 45. Similarly the concentration of total HCH varied from 1 to 260 nanograms per gram of milk fat (ng / g). The highest levels of these substances were found in breast milk from immigrants from countries where pesticides are still used.

References

  • C. Thomsen et al. “Determinants of brominated flame retardants in breast milk from a large scale Norwegian study”. Environ Int, 36 (2010) 68-74.
  • M. Eggesbø et al. “Levels of hexachlorobenzene (HCB) in breast milk in relation to birth weight in a Norwegian cohort”. Environ Res, 109 (2009) 559-566.
  • A. Polder et al. “Levels of chlorinated pesticides and polychlorinated biphenyls in Norwegian breast milk (2002-2006), and factors that may predict the level of contamination”. Sci Tot Environ, 407 (2009) 4584-4590.
  • P. Fürst. “Dioxins, polychlorinated biphenyls and other organohalogen compounds in human milk - Levels, correlations, trends and exposure through breastfeeding”. Mol Nutr Food Res 50 (2006) 922-933.
  • H. Stigum et al. “Dioxin and dioxin-like compounds in breast milk from Norwegian mothers”. Organohalogen Comp 67 (2005)1560-1563.
  • G. Becher et al. “Temporal and spatial trends of PCDDs/PCDFs and PCBs in Norwegian breast milk - results from three rounds of WHO coordinated studies”. Organohalogen Comp 56 (2002) 325-328.
  • K. Norén et al. “Certain organochlorine and organobromine contaminants in Swedish human milk in perspective of past 20-30 years”. Chemosphere 40 (2000) 1111-1123.
  • G. Becher et al. “PCDDs, PCDFs, and PCBs in human milk from different parts of Norway and Lithuania”. J Toxicol Environ Health 46 (1995) 433-148.
  • J. Clench-Aas et al. 1988. “Polychlorinated biphenyls (PCBs), dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF) in human milk from three geographic areas in Norway”. Lillestrøm: Norwegian Institute for Air Research. NILU Report 56/88.