Sakrapport till Naturvårdsverkets Miljöövervakning:

Sakrapport till Naturvårdsverkets Miljöövervakning:

Avtalsnummer: Utförare: Programområde:

Delprogram:

215 0312

Livsmedelsverket

Hälsorelaterad miljöövervakning Exponering via livsmedel

Undersökningar/uppdrag: Bröstmjölksstudier – Regionala skillnader

Polyklorerade bifenyler (PCBer), klorerade

bekämpningsmedel, polyklorerade difenyletrar (PBDE) och hexabromcyklododekan (HBCD).

Regionala skillnader i halter av persistenta organiska miljögifter i bröstmjölk från förstföderskor i Uppsala, Göteborg, Lund och Lycksele

2005-06-30

Xxxxx Xxxxxxx0, Xxxxxx Xxxxx0, Xxx Xxx Xxxxxxxx0, Xxxxx Xxxx0, Xxxxxx Xxxxxxxx0, Xxxx Xxxxxxxxx0, Xxxxx Xxxxxxx0

1Livsmedelsverket, Uppsala

2 Institutionen för folkhälsa och klinisk medicin, Umeå Universitet

3Västra Götalandsregionens Miljömedicinska Centrum (VMC), Arbets- och Miljömedicin, Sahlgrenska Universitetssjukhuset, Göteborg

4Avdelningen för Yrkes- och miljömedicin, Universitetssjukhuset i Lund

Sammanfattning

Under perioden 2000-2004 samlades bröstmjölk in från förstföderskor i Uppsala, Göteborg, Lund och Lycksele. Syftet med studien var att undersöka om det finns några regionala skillnader i halter av polyklorerade bifenyler (PCBer), klorerade pesticider/metaboliter (hexaklorbensen (HCB), ß-hexaklorocyklohexan (ß-HCH), oxyklordan, trans-nonaklor, DDT och DDT-metaboliter) och bromerade flamskyddsmedel (polybromerade difenyletrar (PBDE) och hexabromcyklododekan (HBCD)) i bröstmjölk. Resultaten från studien kommer att användas vid riskvärdering av miljöföroreningar i livsmedel, samt vid riskvärdering av spädbarns exponering under fosterstadiet och amningsperioden.

Efter justering för faktorer som är kända för att påverka halten av organiska miljöföroreningar i bröstmjölk (ålder, BMI (body mass index), viktsuppgång under graviditet etc.) kunde vissa signifikanta regionala skillnader i halter av de studerade substanserna observeras.

Skillnaderna var dock små, och inga säkra slutsatser om orsaker till skillnaderna kan dras.

De justerade geometriska medelhalterna av vissa PCB-kongener i bröstmjölk var något lägre i Göteborg och högre i Lund och Lycksele jämfört med Uppsala. Den största skillnaden visades för CB 167, vars justerade medelhalt var två gånger högre i Lund jämfört med Göteborg.

Även för de klorerade pesticiderna var skillnaderna i medelhalter mellan de olika regionerna små. De justerade medelhalterna av ß-HCH, trans-nonaklor och p,p’-DDT var något lägre i bröstmjölk från kvinnor i Göteborg jämfört med Uppsala och den justerade medelhalten av ß- HCH var högre i Lund jämfört med Uppsala. Generellt observerades tendenser till en U- formad syd-nord trend, med de högsta halterna av PCBer och klorerade pesticider i Lund och Lycksele och lägre halter i Göteborg och Uppsala. Orsakerna till dessa regionala skillnader är fortfarande oklara.

Små skillnader i halter av PBDE i de olika regionerna kunde visas. Den största skillnaden observerades för BDE 99, vars justerade medelhalt var 72% högre i Lycksele jämfört med Lund. För BDE 47, 99, 100 och 153 påvisades en signifikant positiv syd-nord trend. Studien är inte tillräckligt omfattande för att orsakerna till denna trend ska kunna identifieras. Inga regionala skillnader i halter av HBCD i bröstmjölk kunde observeras.

Report to the Swedish Environmental Protection Agency, 2005-06-30

Xxxxx Xxxxxxx, Xxxxxx Xxxxx, Xxx Xxx Xxxxxxxx, Xxxxx Xxxx, Xxxxxx Xxxxxxxx, Xxxx Xxxxxxxxx, Xxxxx Xxxxxxx

Regional differences in levels of persistent organic pollutants in breast milk from primipara women in Uppsala, Göteborg, Lund and Lycksele (Sweden)

Introduction

Exposure estimation is an important part of risk assessment of environmental pollutants in food. Among the Swedish human population, food is the major source of exposure to persistent organic pollutants (POPs), such as polychlorinated biphenyls (PCBs) and chlorinated pesticides. These compounds are lipophilic and accumulate in the lipid compartment of the human body. Because of the relatively high lipid content, breast milk is a good matrix for analysis of POP levels. The POP levels in breast milk also reflect the long- term exposure of the individual mother to the persistent POPs and give information about body burden of POPs at the time of pregnancy and nursing.

In order to estimate the temporal trends of the body burden of POPs among pregnant and breast feeding women, and to estimate the intake of the compounds by breast feeding infants recurrent measurements of levels of POPs in human breast milk have been made in the Uppsala region of Sweden since 1996. Trends (1996-2003) of decreasing levels of PCBs and chlorinated pesticides in breast milk from primipara women in Uppsala County have been reported earlier (Lignell et al. 2004). In order to investigate possible regional differences in POP levels in Swedish breast milk, samples were collected from primipara mothers in Göteborg (on the west coast of Sweden) 2001, Lund (southern Sweden) 2003, and Lycksele (northern Sweden) 2003-2004. Substances studied were PCBs, chlorinated pesticides/metabolites and brominated flame retardants.

Material and methods

Recruitment

Breast milk was exclusively sampled from primipara women in order to minimise variation. Breast-feeding is the major pathway of POP excretion in women, and consequently the POP levels are usually higher in breast milk sampled after the first child is born than in breast milk sampled after subsequent deliveries (Vaz et al. 1993).

Uppsala: Mothers were recruited among women who delivered at Uppsala University Hospital from April 2000 to March 2001, from March 2002 to February 2003, and from January to December 2004. Women who delivered during the first week in every month and on randomly selected days during this week were asked to participate in the breast milk study. 2-3 mothers were recruited every month. In 2000-2001, 67 women were asked to participate in the study and 31 donated milk. In 2002-2003, 49 women were asked to participate and 31 donated milk. In 2004, 51 women were asked to participate and 32 donated milk.

Göteborg: Mothers were recruited among women who delivered at Mölndal hospital in September and October 2001. At 10 occasions a nurse informed all available primiparas about the study. 77 mothers were informed about the study and 37 agreed to participate and later donated milk.

Lund: Mothers were recruited among women who were Swedish by birth and delivered at Lund University Hospital from January to November 2003. All healthy mothers who had normal deliveries were asked to participate. Totally 42 mothers donated breast milk and 36 samples were sent to the NFA for analysis of POPs.

Lycksele: Mothers were recruited among women who were Swedish by birth and delivered at Lycksele Hospital from September 2003 to July 2004. All together 62 healthy mothers who had normal deliveries were asked to participate and 39 mothers donated breast milk.

Breast milk sampling

The mothers sampled milk at home during the third week after delivery (day 14-21 post partum). Milk was sampled during breastfeeding using a manual breast pump and/or a passive breast milk sampler. The women were instructed to sample milk both at the beginning and at the end of the breastfeeding session. The goal was to sample 500 mL from each mother during 7 days of sampling. During the sampling week, the breast milk was stored in the home freezer, in acetone-washed bottles. Newly sampled milk was poured on top of the frozen milk. At the end of the sampling week a nurse visited the mother to collect the bottles.

Data on age, weight, lifestyle, medical history, dietary habits etc. of the mothers were obtained via questionnaires (Table 1).

Analysis

PCBs and chlorinated pesticides were analysed at the NFA using previously described methods (Atuma and Aune 1999; Xxxx et al. 1999). In brief, 3 g of thoroughly homogenized thawed milk was extracted with a mixture of n-hexane/acetone (1:1). The extracted lipid content was determined gravimetrically after evaporation of the solvents and the sample was then treated with sulphuric acid. The PCB fraction in the sample was separated from the bulk of the chlorinated pesticides by column chromatography on silica gel. The analysis of the PCB congeners and the chlorinated pesticides was performed on a gas chromatograph (GC) equipped with dual capillary columns (Ultra-2 and DB-17) and dual electron-capture detectors (ECD).

PBDEs and HBCD were analysed at the NFA using a previously described method (Atuma et al. 2000), with a few modifications. The milk samples were thawed and homogenized, and then 35 g was extracted with a mixture of n-hexane/acetone (1:1). After addition of ethanol (99.5%) to the combined extracts, the solvents were evaporated and the lipid content determined gravimetrically. The fat was then redissolved in n-hexane and treated with sulphuric acid. The PBDEs and HBCD were separated from the dominating PCB congeners over a silica gel column. The purified extract was then analysed by GC/ECD with dual capillary columns (DB-5 and DB-17) or by GC with mass spectrometry operated in electron capture negative ion mode (GC column DB-5MS).

All samples were fortified with internal standards prior to extraction to correct for analytical losses and to ensure quality control. A number of control samples have been analysed

together with the samples to verify the accuracy and precision of the measurements. The laboratory is accredited for analysis of PCBs and chlorinated pesticides in human milk. In the case of levels below the limit of quantification (LOQ), half of this limit was taken as an estimated value in the calculations.

Individual mono- and di-ortho PCB congeners (CB 28, 52, 101, 105, 114, 118, 138, 153, 156,

157, 167, 170 and 180) and chlorinated pesticides (hexachlorobenzene (HCB), - hexachlorocyclohexane ( HCH), oxychlordane, trans-nonachlor, p,p'-DDE, p,p'-DDT, o,p'- DDT and p,p'-DDD) were analysed in 206 samples, polybrominated diphenyl ethers (BDE

28, 47, 66, 99, 100, 138, 153, 154) in 198 samples and hexabromocyclododecane (HBCD) in

178 samples.

Statistics

Lipid adjusted breast milk POP concentrations were used in the analysis. Women who were not Swedish by birth (N=3) were excluded from the statistical analysis. Levels of CB 52, 101, 114 and 157 were low (>50% below LOQ) and were therefore omitted from the statistical analysis. For the same reason, o,p'-DDT and p,p'-DDD (>95 % below LOQ) as well as BDE 28, 66, 154 and 138 (>50 % below LOQ) were omitted. The distributions of the organochlorine analytical results closely followed a lognormal distribution, therefore all statistical analysis were performed on logarithmically transformed data.

Statistical analysis was performed in MINITAB® for Windows 12.22. Stepwise linear regression was used for selection of independent variables for the regression model. A cutoff value of F=4 was used in order to eliminate independent variables that were not associated to the dependent variable. Multiple linear regression were then used to investigate possible associations between POP levels and sampling locality, with regression models including the independent variables selected in the stepwise procedure. In the analysis, observations with a standard residual of >3 were excluded due to a large influence on the regression results. Also observations with a standard residual <3 were excluded when the computer program indicated that the observation had a large influence on the results for other reasons than a large standard residual.

In the analysis of regional differences in breast milk levels Uppsala was used as the reference region due to the much larger number of observations from that region. Independent variables used in the regression analysis were sampling year, age of the mother (years), body mass index (BMI, kg/m2) before pregnancy, body weight change during pregnancy (% change of initial body weight per week during pregnancy) and after delivery (% weight reduction from delivery to sampling), smoking during pregnancy (never smoked, stopped smoking before pregnancy, smoked during pregnancy) and education (max 4 year high school, 1-3 years higher education, >3 years higher education) (Table 1). Adjusted geometrical means were obtained using the GLM procedure. A regional south-north trend analysis was performed by including the four studied regions as a continuous variable, in which Lund was assigned the value 1, Göteborg 2, Uppsala 3 and Lycksele 4.

Results and discussion

Characteristics of the participants

Characteristics of the participating mothers are compiled in Table 1. Women who were not Swedish by birth (N=3) were excluded from the statistical analysis. The median ages of the mothers varied between 27.1 (Lund 2003-2004) and 30.1 (Uppsala 2000-2001) years.

POP-levels in breast milk

Breast milk concentrations of POPs are shown in Table 2. Among the PCB congeners, the di- ortho congener CB 153 showed the highest median concentrations (31-55 ng/g lipid) in breast milk followed by the di-ortho congeners CB 138 (18-25 ng/g lipid) and CB 180 (15-23 ng/g lipid). Among the mono-ortho congeners CB 114 showed the lowest median concentrations (0.3-0.4 ng/g lipid) and CB 118 the highest (5.6-9.7 ng/g lipid). Overall, the median concentrations of CB 28, 52, 101, 105, 114, 157 and 167 were close to the LOQ. The median levels of mono-orto TEQ and sumPCB were 2.4-3.5 pg/g lipid and 83-140 ng/g lipid respectively.

p,p'-DDE was the compound with the overall highest median concentrations (46-78 ng/g lipid) (Table 2). Levels of o,p'-DDT and p,p'-DDD were low (>95 % below LOQ, results not shown). The median concentrations of the other chlorinated pesticides and metabolites (HCB,

-HCH, oxy-chlordane, trans-nonachlor and p,p'-DDT) varied between 2.5 and 14 ng/g lipid.

The median levels of PCBs and chlorinated pesticides/metabolites found in our study are lower than median levels found in breast milk from primiparous women in Uppsala 1996- 1999 (Aune et al. 1999), and lower than the average levels in pooled breast milk samples from Stockholm 1994-1997 (Xxxxx and Meironyte 2000). This is not surprising since the mean levels of PCBs and chlorinated pesticides/metabolites have continuously declined in breast milk in the Stockholm/Uppsala area since the 1970s (Lignell et al. 2004; Xxxxx and Xxxxxxxxx 2000; Xxx et al. 1993).

Among the PBDE congeners, BDE 47 showed the highest median concentrations (1.2-1.8 ng/g lipid) whereas median levels of BDE 28, 66, 138 and 154 were close to the LOQ ( 0.05-

0.10 ng/g lipid) (Table 2). Median levels of sumPBDE and HBCD were 2.5-3.4 and 0.25-0.39 ng/g lipid respectively. Four mothers from Lycksele had BDE 47 levels >20 ng/g lipids. These mothers also had elevated levels of the other analysed PBDE congeners, with the exception of BDE 183 and in some cases BDE 66 and BDE 138. The median levels of HBCD in breast milk were generally below 1 ng/g lipid in the studied regions.

In the Stockholm area, PBDE levels in pooled breast milk samples increased exponentially between 1972 and 1997 (Xxxxx and Meironyte 2000), but recently the levels seems to have been stabilised (Meironyte 2002). The levels in our study were similar to those found in the Stockholm area 1998-2000 (Meironyte 2002) and in the Uppsala area 1996-2001 (Lind et al. 2002). We can not draw firm conclusions about the reasons behind the higher PBDE levels in the four women from Lycksele. The professions of the women did not reveal any possibilities of high exposures. Three of the women worked in health and child-care, as did many other of the participating women from Lycksele. The only factor that hypothetically could have played a role is that one of the women recently had lived in North America. Human exposure to PBDE is considerably higher in North America than in Sweden, for reasons still unknown (Schecter et al. 2003). We had the hypothesis that recently purchased cars or upholstered furniture could be potential exposure sources, but preliminary analysis of the results from questions about cars and furniture did not reveal any significant associations.

To our knowledge there are no published reports on HBCD levels in breast milk. Our results show that humans are exposed to HBCD and that the compound is transferred to breast milk. The levels are in the same order of magnitude as single PBDE congeners.

Table 1. Characteristics of the mothers participating in the study.

	Uppsala 2000-2001			Uppsala 2002-2003			Uppsala 2004			Göteborg 2001			Lund	2003		Lycksele 2003-2004
	N	Median	Range	N	Median	Range	N	Median	Range	N	Median	Range	N	Median	Range	N	Median	Range
Age of the mother	31	30.1	21-37	31	29.8	24-37	32	29.3	21-35	37	30.0	19-40	36	29.0	25-39	39	27.1	19-35
(years)
BMI before pregnancy	31	22.7	16-37	31	21.6	18-26	32	22.2	18-34	37	22.6	17-42	36	22.8	18-47	39	22.5	18-46
(kg/m2)
Weight gain during pregnancy	31	0.62	0.03-1.5	31	0.63	0.3-0.9	31	0.65	0.09-1.2	37	0.63	0.0-1.1	36	0.58	0.05-1.1	39	0.58	-0.16-1.5
(%/week) a
Weight reduction from delivery	30	9.2	1.3-17	29	8.2	3.1-17	31	10.8	4.5-17	36	9.6	1.5-19	35	9.4	-0.4-17	39	9.0	0.0-14
to sampling (%)b
	N %			N %			N %			N %			N %			N %
Country of birth
Nordic	29	94		31	100		32	100		36	97		36	100		39	100
Non-Nordic	2	6		0	0		0	0		1	3		0	0		0	0
Smoking during pregnancyc
Non-smoker	26	84		25	81		24	75		30	81		30	83		31	79
Former smoker	2	6		2	6.5		4	12.5		2	5		5	14		5	13
Smoker	3	10		4	13		4	12.5		5	14		1	3		3	8
Education
Max 3-4 yr high school	9	29		9	29		9	29		8	22		9	25		23	59
1-3 yr higher education	8	26		5	16		6	19		15	40		5	14		11	28
>3 yr higher education	14	45		17	55		16	52		14	38		22	61		5	13

a% of weight before pregnancy/week of pregnancy.

bWeight reduction minus birth weight of the child in % of weight just before delivery.

cWomen who stopped smoking before pregnancy are considered to be former smokers, and women who stopped smoking during the first or second month of pregnancy are considered to be smokers.

Table 2. Concentrations of PCBs, chlorinated pesticides/metabolites and brominated flame-retardants in breast milk (ng/g milk lipid). Concentrations <LOQ were set to 1/2 LOQ in the calculations of mono-orto-TEQ, sums, medians and ranges.

	Uppsala 2000-2001			Uppsala 2002-2003			Uppsala 2004			Göteborg 2001			Lund	2003		Lycksele 2003-2004
	N	Median	Range	N	Median	Range	N	Median	Range	N	Median	Range	N	Median	Range	N	Median	Range
PCBs
CB 28	31	1.89	0.55-4.83	31	1.33	0.30-8.09	32	1.92	0.43-3.50	37	1.23	0.25-3.31	36	1.68	0.58-24.4	39	1.23	0.35-6.45
CB 52	31	0.45	0.20-1.31	31	0.35	0.20-0.65	32	0.38	0.24-0.67	37	0.35	0.15-0.78	36	0.32	0.18-1.03	39	0.33	0.20-0.66
CB 101	31	0.60	0.20-2.23	31	0.40	0.20-1.00	32	0.38	0.24-0.69	37	0.40	0.20-2.81	36	0.34	0.18-1.03	39	0.35	0.20-0.80
CB 105	31	1.12	0.2-3.72	31	1.15	0.63-3.06	32	0.47	0.29-2.58	37	0.79	0.25-25.6	36	1.06	0.29-3.58	39	0.66	0.22-2.78
CB 114	31	0.35	0.20-1.48	31	0.40	0.20-1.07	32	0.37	0.24-0.55	37	0.35	0.20-2.34	36	0.33	0.22-1.02	39	0.32	0.20-0.78
CB 118	31	9.66	4.48-25.6	31	7.76	3.83-16.2	32	6.72	2.85-13.6	37	8.41	2.91-102	36	7.52	3.87-18.5	39	5.63	2.55-15.6
CB 138	31	24.6	12.3-45.8	31	23.3	11.1-47.3	32	19.1	7.76-36.6	37	24.0	8.76-88.4	36	23.6	10.4-53.7	39	18.3	6.53-55.3
CB 153	31	55.2	20.6-116	31	43.1	21.8-97.3	32	35.4	11.6-66.5	37	48.4	12.5-188	36	43.4	24.5-95.4	39	31.2	13.6-113
CB 156	31	3.39	1.50-8.19	31	2.80	0.65-7.77	32	3.33	0.45-6.76	37	4.02	0.81.12.0	36	3.91	2.02-9.48	39	2.8	1.00-8.60
CB 157	31	0.85	0.35-2.60	31	0.45	0.20-1.85	32	0.43	0.25-1.17	37	0.78	0.20-2.63	36	0.51	0.22-1.80	39	0.37	0.22-1.34
CB 167	31	1.70	0.50-4.16	31	0.94	0.30-1.97	32	1.14	0.33-2.22	37	1.10	0.25-3.16	36	1.25	0.49-2.87	39	0.84	0.28-1.81
CB 170	31	10.9	4.76-25.6	31	9.37	4.90-19.7	32	7.47	2.62-19.9	37	10.4	2.35-40.6	36	9.66	4.81-38.6	39	6.48	2.86-27.1
CB 180	31	22.4	10.7-56.1	31	20.4	10.9-46.5	32	17.1	5.02-44.5	37	23.2	4.86-83.5	36	21.2	10.8-72.9	39	15.0	6.17-58.6
mono-ortho TEQa	31	3.43	1.56-8.95	31	2.71	1.44-6.79	32	2.95	1.01-5.39	37	3.50	0.97-17.9	36	3.12	1.78-8.12	39	2.40	1.13-5.66
SumPCBb	31	140	58.3-290	31	111	56.4-241	32	96.2	35.0-184	37	129	34.7-456	36	114	67.6-271	39	83.3	38.0-272
Pesticides and metabolites
HCB	31	13.7	9.40-29.5	31	8.81	6.34-20.6	32	10.4	3.97-16.6	37	11.8	5.86-25.9	36	11.4	7.42-19.7	39	9.01	4.43-17.6
-HCH	31	9.71	5.16-127	31	7.23	4.61-24.6	32	7.80	2.72-20.7	37	9.59	3.13-104	36	8.39	5.31-42.6	39	5.31	2.32-16.2
oxy-chlordane	31	3.55	2.00-21.2	31	3.12	1.74-8.51	32	2.92	1.05-9.13	37	3.36	1.17-10.5	36	2.83	1.55-7.21	39	2.46	1.10-5.46
trans-nonachlor	31	6.51	2.88-30.9	31	5.75	2.45-12.7	32	4.64	1.68-12.7	37	5.93	1.52-20.5	36	4.87	2.33-14.1	39	3.63	1.28-9.61
p,p´-DDE	31	77.5	32.2-894	31	59.0	24.9-176	32	61.9	20.2-174	37	71.9	17.0-718	36	63.7	18.5-209	39	46.2	14.6-149
p,p´-DDT	31	5.18	1.69-19.6	31	4.22	2.19-10.7	32	3.73	0.84-33.8	37	3.69	1.05-31.3	36	4.15	0.68-14.4	39	2.59	0.57-7.79
Brominated flame-retardants
BDE 28	31	0.07	0.03-0.23	30	0.10	0.05-0.31	29	0.07	0.04-0.60	33	0.06	0.04-1.58	36	0.07	0.03-0.37	39	0.10	0.04-4.22
BDE 47	31	1.66	0.63-6.03	30	1.30	0.55-6.80	29	1.41	0.61-12.0	33	1.30	0.55-8.94	36	1.16	0.33-9.32	39	1.81	0.66-73.0
BDE 66	31	0.05	0.03-0.09	30	0.06	0.04-0.10	29	0.06	0.04-0.13	33	0.05	0.02-0.17	36	0.05	0.03-0.27	39	0.05	0.04-0.97
BDE 99	31	0.15	0.06-0.61	30	0.19	0.07-0.61	29	0.35	0.19-5.21	33	0.24	0.07-0.72	36	0.26	0.05-1.41	39	0.48	0.15-17.0
BDE 100	31	0.27	0.07-0.78	30	0.28	0.07-1.80	29	0.28	0.07-2.07	33	0.24	0.05-0.62	36	0.27	0.04-1.10	39	0.36	0.09-17.6
BDE 138	31	0.05	0.03-0.09	30	0.05	0.03-0.10	29	0.06	0.04-0.09	33	0.05	0.02-0.12	36	0.05	0.03-0.08	39	0.05	0.03-0.18
BDE 153	31	0.61	0.24-1.33	30	0.66	0.38-2.30	29	0.68	0.25-4.61	33	0.53	0.24-1.04	36	0.61	0.23-1.90	39	0.62	0.06-7.99
BDE 154	31	0.06	0.03-0.28	30	0.06	0.03-0.14	29	0.06	0.04-0.36	33	0.05	0.02-0.12	36	0.05	0.03-0.08	39	0.05	0.04-0.94
sumPBDEc	31	3.25	1.32-8.39	30	2.87	1.61-12.1	29	3.13	1.59-21.6	33	2.54	1.42-12.2	36	2.63	0.92-12.9	39	3.36	1.29-107
HBCD	11	0.25	0.15-0.45	30	0.35	0.10-1.50	29	0.33	0.14-4.36	33	0.30	0.15-2.37	36	0.44	0.11-5.94	39	0.39	0.09-10.4

apg/g milk lipid, including CB105, 114, 118, 156, 157 and 167 TEQs.

bincluding CB 28, 52, 101, 105, 114, 118, 138, 153, 156, 157, 167, 170 and 180.

cincluding BDE 28, 47, 66, 99, 100, 138, 153 and 154.

Regional differences

Multiple linear regressions showed that the adjusted geometric means of some of the PCBs were significantly lower in milk from women in Göteborg (CB 105, 118 and CB 167) compared to Uppsala and higher in milk from women in Lund (CB 138, 156, 167, 170, 180, mono-ortho TEQ) and Lycksele (CB 138, 156, 170, mono-ortho TEQ and sumPCB) compared to Uppsala (Table 3). The largest difference was found for CB 167, where Lund had a two-fold higher adjusted mean than Göteborg. Thus the differences were not large, showing that Swedish women in child-bearing age in general have been exposed to similar levels of the compounds.

Similarly, we found no large differences in levels of chlorinated pesticides/metabolites between the regions, although the adjusted geometric means of -HCH, trans-nonachlor and p,p'-DDT in breast milk were significantly lower from women in Göteborg compared to Uppsala. Moreover, the adjusted geometric mean of -HCH was significantly higher in Lund compared to Uppsala (Table 4). -HCH also showed the largest regional difference with a 1.3-fold higher adjusted mean in Lund than in Göteborg.

A few earlier studies have tried to determine if there are regional differences in breast milk levels of PCB and chlorinated pesticides/metabolites in Sweden (Atuma et al. 1998; Noren 1983; Vaz et al. 1993). None of the studies could, however, draw firm conclusions about regional differences, due to a small number of samples and lack of information about the personal characteristics of the participating women. In a study of organochlorine levels in serum from older Swedish women (50-74 years) living in counties along the east coast and Lake Vättern (Malmö, Linköping, Uppsala, Umeå regions), multiple regression analysis showed that the adjusted means of CB 153, CB 156, CB 180, HCB, -HCH, and

oxychlordane in serum lipids tended to follow a U-shaped south-north trend, with the Malmö and Umeå regions having the highest adjusted means and the Linköping and Uppsala regions having the lowest means (Glynn et al. 2003). Similarly, in our study the women in Lund and Lycksele tended to have higher adjusted means of PCBs and chlorinated pesticides/metabolites in their breast milk than the Uppsala women. The Göteborg area was not represented in the study of elderly women, but in our study women from this area consistently had the lowest adjusted means of the organochlorines.

We can not draw firm conclusions about the reasons behind the regional differences in organochlorine levels in breast milk. The regression models, used in the adjustment of the results, could explain 11-72% of the variation in PCB and chlorinated pesticide/metabolite levels. We found the highest percentage of explained variation among the higher chlorinated PCBs and the lowest percentage among the lower chlorinated PCBs. There still is a significant part of the variation that we could not account for in the regression models. One possible factor is organochlorine levels in food. Food has been the major source of exposure to organochlorines after the use and production of organochlorines were banned, starting in the early 1970s. In a study of CB 153, HCB and p,p'-DDE levels in adipose tissue of bovines and swine in Sweden 1994-2003, levels of CB 153 and p,p'-DDE were higher in southern Sweden than in the central and northern part of the country (Glynn et al. 2005). We did, however, not find this contamination pattern in breast milk, so other unexplained life-style factors and personal characteristics than exposure from meat and milk products must play a more important role in determining the organochlorine levels in breast milk.

Linear regression analysis showed that some regions had significantly lower or higher adjusted mean levels of PBDEs than the Uppsala region (Table 5). The differences were however not large. BDE 99 was the congener that showed the largest differences, in this case a 72% higher adjusted mean was found in Lycksele compared to Lund. For all four PBDE congeners a significant positive south-north trend of increasing adjusted mean levels was shown (Table 5). Our results are not comprehensive enough to draw conclusions about the factors behind this trend. The regression models used generally explained only a small part of the variation in PBDE levels (R2<30%).

We found no regional differences in adjusted mean levels of HBCD and no south-north trend (Table 5). The regression model only explained 8% of the variation in HBCD levels.

Table 3. Adjusted geometric means of PCBs in breast milk (ng/g lipid) from primipara women living in Uppsala 2000-2004, Göteborg 2001, Lund 2003 and Lycksele 2003-2004 (N=188-201)

Compound	Locality	Mean (± SD)	Pa	Ind. variablesb	R2 (%)
CB 28	Uppsala	1.34 (1.22-1.48)		Sampling year,	11.2
				smoking,
	Göteborg	1.06 (0.93-1.21)	0.075	education
	Lund	1.43 (1.25-1.65)	0.623
	Lycksele	1.36 (1.18-1.57)	0.928
CB105	Uppsala	0.84 (0.79-0.89)		Sampling year, age of	26.3
				the
	Göteborg	0.64 (0.57-0.71)	0.023	mother
	Lund	0.93 (0.84-1.02)	0.408
	Lycksele	0.94 (0.85-1.05)	0.360
CB 118	Uppsala	7.65 (7.38-7.93)		Sampling year, age of	42.2
				the
	Göteborg	6.33 (5.94-6.75)	0.008	mother, weight gain
				during
	Lund	7.71 (7.27-8.17)	0.915	pregnancy
	Lycksele	7.87 (7.40-8.37)	0.706
CB 138	Uppsala	21.0 (20.4-21.6)		Sampling year, age of	53.1
				the
	Göteborg	19.4 (18.4-20.4)	0.162	mother, weight gain
				during
	Lund	23.6 (22.5-24.7)	0.032	pregnancy, BMI
	Lycksele	23.7 (22.6-24.9)	0.038
CB 153	Uppsala	40.5 (39.5-41.6)		Sampling year, age of	67.7
				the
	Göteborg	37.4 (35.7-39.2)	0.125	mother, weight gain
				during
	Lund	43.9 (42.1-45.9)	0.115	pregnancy, BMI,
				weight
	Lycksele	44.0 (42.0-46.1)	0.146	reduction after delivery
CB 156*	Uppsala	3.08 (2.98-3.18)		Sampling year, age of	58.0
				the
	Göteborg	3.10 (2.93-3.27)	0.945	mother, weight gain
				during
	Lund	4.01 (3.81-4.22)	<0.001	pregnancy, BMI,
				weight
	Lycksele	3.75 (3.54-3.97)	0.005	reduction after delivery
CB 167	Uppsala	1.03 (0.99-1.08)		Sampling year, age of	44.8
				the
	Göteborg	0.69 (0.64-0.75)	<0.001	mother
	Lund	1.36 (1.26-1.46)	0.002
	Lycksele	1.11 (1.03-1.20)	0.405
CB 170	Uppsala	8.71 (8.47-8.95)		Sampling year, age of	70.9
				the
	Göteborg	8.83 (8.41-9.27)	0.795	mother, weight gain
				during
	Lund	9.83 (9.39-10.3)	0.026	pregnancy, BMI,

weight

Lycksele 9.83 (9.34-10.3) 0.044 reduction after delivery

CB 180	Uppsala Göteborg Lund Lycksele	19.3 (18.7-19.8) 19.2 (18.3-20.1) 21.4 (20.4-22.3) 21.1 (20.1-22.1)	0.960 0.048 0.123	Sampling year, age of the mother, weight gain during pregnancy, BMI, weight reduction after delivery	72.2
mono-orto TEQ	Uppsala Göteborg Lund Lycksele	2.86 (2.78-2.94) 2.69 (2.56-2.83) 3.48 (3.32-3.64) 3.50 (3.33-3.68)	0.258 <0.001 0.001	Sampling year, age of the mother, weight gain during pregnancy, BMI, weight reduction after delivery	60.1
(pg/g milk lipid)
sumPCB	Uppsala Göteborg Lund Lycksele	107 (104-109) 98.1 (94.0-102) 117 (112-122) 118 (113-123)	0.073 0.055 0.047	Sampling year, age of the mother, weight gain during pregnancy, BMI, weight reduction after delivery	71.2

aSignificance level in comparison to Uppsala

bIndependent variables in the linear regression model used in adjustment of geometrical means.

*Statistically significant south-north trend in breast milk levels.

Table 4. Adjusted geometric means of chlorinated pesticides in breast milk (ng/g lipid) from primipara women living in Uppsala 2000-2004, Göteborg 2001, Lund 2003 and Lycksele 2003-2004 (N=192-200).

Compound	Locality	Mean (± SD)	Pa	Ind. variablesb	R2 (%)
HCB	Uppsala	10.6 (10.3-10.8)		Sampling year, age of	36.5
				the
	Göteborg	9.73 (9.32-10.2)	0.081	mother, weight gain
				during
	Lund	11.5 (11.1-12.0)	0.066	preg., weight reduction
	Lycksele	11.4 (11.0-11.9)	0.136	after delivery
-HCH*	Uppsala	7.65 (7.37-7.95)		Sampling year, age of the	58.9
	Göteborg	6.77 (6.38-7.19)	0.038	mother, smoking
	Lund	9.02 (8.55-9.51)	0.004
	Lycksele	7.53 (7.13-7.96)	0.788
oxy-chlordane	Uppsala	3.04 (2.95-3.13)		Sampling year, age of	50.9
				the
	Göteborg	2.71 (2.58-2.86)	0.051	mother, weight gain
				during
	Lund	2.93 (2.80-3.08)	0.542	pregnancy, BMI,
				weight
	Lycksele	3.38 (3.20-3.56)	0.096	reduction after delivery
trans-nonachlor	Uppsala	5.19 (4.99-5.39)		Sampling year, age of	46.5
				the
	Göteborg	4.42 (4.14-4.73)	0.033	mother, BMI
	Lund	4.98 (4.68-5.30)	0.586
	Lycksele	5.04 (4.71-5.40)	0.726
p,p´-DDE	Uppsala	63.9 (61.0-66.9)		Sampling year, age of	38.0
				the
	Göteborg	58.3 (53.8-63.1)	0.308	mother, education
	Lund	64.8 (60.2-69.8)	0.875
	Lycksele	67.1 (61.8-72.8)	0.611
p,p´-DDT	Uppsala	4.16 (3.95-4.38)		Sampling year, age of	35.7
				the
	Göteborg	3.39 (3.10-3.71)	0.044	mother, education
	Lund	4.34 (3.99-4.72)	0.665
	Lycksele	3.37 (3.08-3.70)	0.055

aSignificance level in comparison to Uppsala

bIndependent variables in the linear regression model used in adjustment of geometrical means.

*Statistically significant south-north trend in breast milk levels.

Table 5. Adjusted geometric means of polybrominated diphenyl ethers and hexabromocyclo- dodecane in breast milk (ng/g lipid) from primipara women living in Uppsala 2000-2004, Göteborg 2001, Lund 2003 and Lycksele 2003-2004.

Compound	Locality	Mean (± SD)	Pa	Ind. variablesb	R2
PBDE 47*	Uppsala	1.46 (1.34-1.59)		BMI, smoking	11%
	Göteborg	1.33 (1.18-1.51)	0.478
	Lund	1.08 (0.95-1.22)	0.014
	Lycksele	1.70 (1.50-1.93)	0.226
PBDE 99*	Uppsala	0.25 (0.23-0.28)		BMI, smoking, age of	8%
	Göteborg	0.27 (0.24-0.31)	0.626	the mother.
	Lund	0.23 (0.21-0.27)	0.567
	Lycksele	0.43 (0.38-0.49)	<0.001
PBDE 100*	Uppsala	0.29 (0.27-0.31)		Sampling year, weight	29%
	Göteborg	0.25 (0.22-0.28)	0.324	change during preg.
	Lund	0.25 (0.24-0.27)	0.365
	Lycksele	0.38 (0.33-0.43)	0.090
PBDE 153*	Uppsala	0.63 (0.61-0.66)		BMI, weight change	18%
	Göteborg	0.52 (0.49-0.55)	0.009	during preg.
	Lund	0.60 (0.56-0.64)	0.476	.
	Lycksele	0.64 (0.60-0.68)	0.832
HBCD	Uppsala	0.28 (0.27-0.31)		BMI, sampling year,	8%
	Göteborg	0.35 (0.31-0.39)	0.109	smoking
	Lund	0.34 (0.31-0.38)	0.082
	Lycksele	0.34 (0.30-0.37)	0.119

aSignificance level in comparison to Uppsala

bIndependent variables in the linear regression model used in adjustment of geometrical means.

*Statistically significant south-north trend in breast milk levels.

Conclusions

We found statistically significant differences in breast milk levels of PCB, chlorinated pesticides/metabolites, PBDEs and HBCD between the four regions studied (Lund, Göteborg, Uppsala, Lycksele) after adjustment of the results with personal characteristics that could influence breast milk levels. The differences in levels were, however, not large, indicating similar long-term exposure levels of organohalogenated persistent compounds among pregnant and nursing primipara women from different areas of Sweden.

Due to the complexity of the study and the wealth of data, further analyses will be performed on the collected data set. However, these analyses will not likely change the overall conclusions given above.

Acknowledgements

We thank the participating mothers for their patience and dedication during the study. The midwives and other personnel involved in sampling, analysis, interviewing and administration are acknowledged for good collaboration.

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