Ambiente e tiroide: effetti degli inquinanti industriali sulla funzionalità tiroideaPaolo Emidio MacchiaDipartimento di Medicina Clinica e Chirurgia, Università degli studi di Napoli “Federico II”

L’inquinamento industriale è un fenomeno di immense dimensioni e difficilmente controllabile.Ogni anno vengono rilasciate nell’ambiente oltre 6x1018 tonnellate di prodotti chimici e sonoregistrati circa 3000 nuovi prodotti chimici (molti dei quali difficilmente identificabili in quantocoperti da brevetti). Tutte queste sostanze, una volta disperse nell’ambiente, raggiungono l’uomoattraverso i vari passaggi della catena alimentare. Inoltre, per la maggior parte degli inquinantiindustriali, si verificano i fenomeni di bioaccumulo (deposito in concentrazioni elevate in particolaritessuti, come il tessuto adiposo) e di biomagnificazione (aumento delle concentrazioni tissutali manmano che si sale lungo la catena alimentare).Per alcuni di questi prodotti, come i policlorobifenili (PCBs), polibromodifenileteri (PBDEs) e lediossine gli effetti tossici sulla tiroide sono stati ben caratterizzati. In particolare queste sostanzehanno una struttura chimica simile a quella degli ormoni tiroidei. I meccanismi attraverso i quali gliinquinanti ambientali agiscono sulla funzione tiroidea sono molteplici: stati dimostrati effettibiologici con interferenza sull’espressione dei geni coinvolti nella biosintesi degli ormoni tiroidei, sultrasporto dello iodio, sulle proteine di trasporto degli ormoni tiroidei nel torrente circolatorio, esull’attivazione o sull’eliminazione degli ormoni tiroidei. Inoltre PCB e PBDE possono anchecompetere per il legame degli ormoni tiroidei al loro recettore.L’esposizione a concentrazioni elevate di queste sostanze in animali da esperimento o in animali chevivono in aree con alta presenza di inquinanti industriali determina una riduzione dei livelli di ormonitiroidei circolanti e, in alcuni casi, quadri istologici di gozzo. Effetti analoghi sono anche statiriscontrati nell’uomo: un interessante studio italiano ha evidenziato valori di TSH neonatale più altinelle aree della zona di Seveso maggiormente esposte alla contaminazione con diossinaconseguente all’incidente del 10 luglio 1976 nell'azienda ICMESA.In conclusione, vi sono numerose evidenze che suggeriscono come gli inquinanti industrialidetermino vari effetti sulla funzione tiroidea. Molti studi sono stati effettuati in vitro ma alcuneevidenze in vivo vanno nelle stesse direzioni. Ovviamente i dati sono ancora preliminari e,soprattutto, nei vari modelli sperimentali non vengono prese in considerazione le possibiliinterazioni con l’ambiente (ed in particolare lo iodio, che rappresenta il principale interferenteendocrino per la tiroide), le interazioni tra inquinanti diversi, e soprattutto le modalità ed i tempi diesposizione. Tutti questi parametri certamente modulano gli effetti biologici sulla tiroide, e pertantoulteriori studi sono necessari per iniziare a comprendere il vero ruolo dell’inquinamento ambientalenei confronti della ghiandola tiroidea.

The enviroment and thyroid:from the prenatal exposure to pollution to the

nutrition impact on thyroid status in adultsPaolo E. Macchia

Dipartimento di Medicina Clinica e ChirurgiaUniversità degli Studi di Napoli “Federico II”

I° meetingClub SIE Endocrinologia Ambientale

09.00 - 11.00 Arrivo ed iscrizione dei partecipanti

11.00 - 11.15 Inaugurazione: A. Lenzi (UniRoma1) e A. Colao (UniNA)

11.15 - 11.30 Salutid el le aut oritàTBC

11.30 - 12.00 Interventip r eordinatiChair:W. Ricciardi (ISS) - G. Novelli (UniRoma2)Referenti

per il CNBBS V di:

Ministero della Salute - E. CecereMinistero dell’Ambiente e della Tutela del Territorioe del Mare - C. ZaghiIstit

u

t o Superiore di Sanità - A. MantovaniEnte Nazionale Energia Atomica - C. Marino

ENDO2.0

SOCIETA

IT.ENDOCRINOLOGIA

AWEEKOFENDOC

RIN

OLOGY

SIE2017

Roma, 19 giugno 2017

Sala Polifunzionale PCMVia Santa Maria in via 39

I° meetingClub SIE Endocrinologia Ambientale

09.00 - 11.00 Arrivo ed iscrizione dei partecipanti

11.00 - 11.15 Inaugurazione: A. Lenzi (UniRoma1) e A. Colao (UniNA)

11.15 - 11.30 Salutid el le aut oritàTBC

11.30 - 12.00 Interventip r eordinatiChair:W. Ricciardi (ISS) - G. Novelli (UniRoma2)Referenti

per il CNBBS V di:

Ministero della Salute - E. CecereMinistero dell’Ambiente e della Tutela del Territorioe del Mare - C. ZaghiIstit

u

t o Superiore di Sanità - A. MantovaniEnte Nazionale Energia Atomica - C. Marino

ENDO2.0

SOCIETA

IT.ENDOCRINOLOGIA

AWEEKOFENDOC

RIN

OLOGY

SIE2017

Roma, 19 giugno 2017

Sala Polifunzionale PCMVia Santa Maria in via 39

I° meeting Club SIE Endocrinologia AmbientaleRoma, 19 giugno 2017

Sala Polifunzionale PCMVia Santa Maria in via 39

Inquinanti industriali

• 6 x 1018 di tonnellate di prodottichimici prodotti annualmente

• 2.000-3.000 nuovi prodotti chimiciregistrati ogni anno

• 2/3 di quelli sviluppati dal 1983indicati come "segreti commerciali",rendendo difficile l'indagine

• 85.000 noti o fortemente sospettidi essere tossici per la salute

• Più del 90% non è mai statosottoposto a screening per latossicità

0,1

1

10

100

1000

1930 1950 1970 1990 2000M

ilion

i di t

onne

llate

Anno

Produzione mondiale di composti chimici

Modalità di contaminazione all’uomo

Dispersione

SorgentiTrasporto

Deposito

Passaggio aglialimenti

Erosionedel suolo

Combustione

Processiindustriali

Scaricodiretto

Bioaccumulo

• Aumento della concentrazione diuna sostanza chimica in organi otessuti specifici ad un livellosuperiore a quello previstonormalmente.

• Le sostanze chimiche tossichesolubili in acqua vengonosolitamente escrete nelle urine

• Oli e tossine lipo-solubili si accumulano nei depositi di grassoe rimangono a lungo nel corpo (tempo di permanenza)

Biomagnificazione

• Le tossine vengono concentratenei vari passaggi lungo la lacatena alimentare

• DDT, PCB

• Sono immagazzinate nel grassocorporeo e influenzano alcunefasi della la gestazione o durantela posa dell'uovo e la crescita.

Policlorobifenili (PCBs)

• Utilizzati, a partire dagli anni ‘70, comeisolanti per apparecchiature elettriche edelettroniche

• Scarsamente solubili in acqua, molto solubilinei grassi, resistenti alla degradazionechimica, fisica e biologica.

• Aree maggiormente contaminate(PCB deposit):

• Brescia, Mar Baltico, baia dell’Hudson, GrandiLaghi

• Estremamente persistenti: possibile effettodi “biomagnificazione”

• Oggi utilizzati solo in “sistemi chiusi”

Polibromodifenileteri (PBDEs)

• Sostanze chimiche di produzione industrialeusate per vari scopi commerciali,principalmente come ritardanti di fiamma.

• I possibili congeneri sono 209, differenti pernumero e posizione degli atomi di bromo suidue anelli aromatici.

• Composti piuttosto stabili e molto lipofilici• Sono persistenti nell’ambiente e

bioconcentrano lungo le reti alimentari,accumulandosi nei grassi.

• Struttura simile agli ormoni tiroidei

Diossine

• Famiglia di sostanze chimichestrutturalmente connesseche hanno un meccanismo comunedi azione e induconouno spettro comune di rispostebiologiche

• Mai prodotte intenzionalmente• Sottoprodotti indesiderati di processi

industriali e di combustione• Inquinanti ambientali altamente

persistenti

• Principali sorgenti• Incenerimento di rifiuti non controllato• Combustioni non controllate

• Incendi di foreste o eruzioni vulcaniche• Raffinazione di metalli• Serbatoi ambientali

• Suoli contaminati e sedimenti da precedentidisseminazioni

Inquinanti industriali ed effetti sulla tiroide

• Possibile azione con differenti meccanismi• Discrete evidenze in modelli in vitro ed

animali• Limitati i dati su soggetti umani

PCB e tiroide in modelli animali

L’esposizione di ratti a PCB determina riduzione dei livelli di FT4 e un quadro istologico compatibilecon iperattività ghiandolare

PCB e tiroide in modelli animali

Riduzione degli ormoni circolanti anche in altri modelli animali

PCBs and DDT in the serum of juvenile California sea lions:associations with vitamins A and E and thyroid hormones

Cathy Debiera,* , Gina M . Ylitalob, M ichael Weisec, Frances Gullandd,Daniel P. Costac, Burney J. Le Boeufe, Tanguy de Tillessef, Yvan LarondelleaaUnite de Biochimie de la Nutrition, Universit e catholique de Louvain, Croix du Sud 2/8, B-1348 Louvain-la-Neuve, Belgium

bNOAA Fisheries/Environmental Conservation Division, 2725 Montlake Boulevard East Seattle, WA 98112, USAcDepartment of Ecology and Evolutionary Biology, Center for Ocean Health, 100 Shaffer Road, University of California,

Santa Cruz, CA 95060, USAdThe Marine Mammal Center, Marin Headlands, 1065 Fort Cronkhite, Sausalito, CA 94965, USAeOffice for Research, 401 Clark Kerr Hall, University of California, Santa Cruz, CA 95064, USA

fFaune & Biotopes, Allee de la Peupleraie, B-1300 Wavre, Belgium

Received 23 February 2004; accepted 26 July 2004

Results show high levels of organochlorine contaminants in juvenileCalifornia sea lions and a link between vitamin A, thyroid hormones and PCB exposure.

Abstract

Top-trophic predators like California sea lions bioaccumulate high levels of persistent fat-soluble pollutants that may provokephysiological impairments such as endocrine or vitamins A and E disruption. We measured circulating levels of polychlorinatedbiphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in 12 healthy juvenile California sea lions captured on Ano NuevoIsland, California, in 2002. We investigated the relationship between thecontamination by PCBsand DDT and thecirculating levelsof vitamins A and E and thyroid hormones (thyroxine, T4 and triiodothyronine, T3). Serum concentrations of total PCBs (

PPCBs)

and total DDT were 14G 9mg/kg and 28G 19 mg/kg lipid weight, respectively. PCB toxic equivalents (PPCB TEQs) were

320G 170 ng/kg lipid weight. Concentrations ofPPCBs and

PPCB TEQs in serum lipids were negatively correlated ( p ! 0.05)

with serum vitamin A and T3, potentially reflecting PCB-related toxicity. A slight but not significant negative correlation ( p ! 0.1)was observed between serum T4 and the levels of

PPCBs and

PPCB TEQs. Conversely, no relationship was evident between the

contaminant concentrations and vitamin E ( pO 0.1). As juvenile California sea lions are useful sentinels of coastal contamination,the high levels encountered in their serum is cause for concern about the ecosystem health of the area.Ó 2004 Elsevier Ltd. All rights reserved.

Keywords: California sea lion; PCBs; DDT; Vitamin; Thyroid hormone

1. Introduction

The marine ecosystem of California is highlycontaminated by organochlorine pollutants (OCs) likePCBs and DDT that have been historically discharged

to the Palos Verdes Shelf in southern California (Stullet al., 1996; Zeng and Venkatesan, 1999; Lee andWiberg, 2002). In the early 1970s, California sea lions,Zalophus californianus, contained very high tissue levelsof DDT and PCBs (blubber levels of up to 2700 and145 mg/kg, respectively; Le Boeuf and Bonnell, 1971;DeLong et al., 1973). Since the cessation of DDTmanufacture in theUnited States and thedumping of its

* Corresponding author. Fax: C 32 10 473728.E-mail address: debier@bnut.ucl.ac.be (C. Debier).

0269-7491/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.doi:10.1016/j.envpol.2004.07.012

Environmental Pollution 134 (2005) 323–332www.elsevier.com/locate/envpol

PCB e tiroide in modelli animali

Riduzione degli ormoni circolanti anche in altri modelli animali

PCBs and DDT in the serum of juvenile California sea lions:associations with vitamins A and E and thyroid hormones

Cathy Debiera,* , Gina M . Ylitalob, M ichael Weisec, Frances Gullandd,Daniel P. Costac, Burney J. Le Boeufe, Tanguy de Tillessef, Yvan LarondelleaaUnite de Biochimie de la Nutrition, Universit e catholique de Louvain, Croix du Sud 2/8, B-1348 Louvain-la-Neuve, Belgium

bNOAA Fisheries/Environmental Conservation Division, 2725 Montlake Boulevard East Seattle, WA 98112, USAcDepartment of Ecology and Evolutionary Biology, Center for Ocean Health, 100 Shaffer Road, University of California,

Santa Cruz, CA 95060, USAdThe Marine Mammal Center, Marin Headlands, 1065 Fort Cronkhite, Sausalito, CA 94965, USAeOffice for Research, 401 Clark Kerr Hall, University of California, Santa Cruz, CA 95064, USA

fFaune & Biotopes, Allee de la Peupleraie, B-1300 Wavre, Belgium

Received 23 February 2004; accepted 26 July 2004

Results show high levels of organochlorine contaminants in juvenileCalifornia sea lions and a link between vitamin A, thyroid hormones and PCB exposure.

Abstract

Top-trophic predators like California sea lions bioaccumulate high levels of persistent fat-soluble pollutants that may provokephysiological impairments such as endocrine or vitamins A and E disruption. We measured circulating levels of polychlorinatedbiphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in 12 healthy juvenile California sea lions captured on Ano NuevoIsland, California, in 2002. We investigated the relationship between thecontamination by PCBsand DDT and thecirculating levelsof vitamins A and E and thyroid hormones (thyroxine, T4 and triiodothyronine, T3). Serum concentrations of total PCBs (

PPCBs)

and total DDT were 14G 9mg/kg and 28G 19 mg/kg lipid weight, respectively. PCB toxic equivalents (PPCB TEQs) were

320G 170 ng/kg lipid weight. Concentrations ofPPCBs and

PPCB TEQs in serum lipids were negatively correlated ( p ! 0.05)

with serum vitamin A and T3, potentially reflecting PCB-related toxicity. A slight but not significant negative correlation ( p ! 0.1)was observed between serum T4 and the levels of

PPCBs and

PPCB TEQs. Conversely, no relationship was evident between the

contaminant concentrations and vitamin E ( pO 0.1). As juvenile California sea lions are useful sentinels of coastal contamination,the high levels encountered in their serum is cause for concern about the ecosystem health of the area.Ó 2004 Elsevier Ltd. All rights reserved.

Keywords: California sea lion; PCBs; DDT; Vitamin; Thyroid hormone

1. Introduction

The marine ecosystem of California is highlycontaminated by organochlorine pollutants (OCs) likePCBs and DDT that have been historically discharged

to the Palos Verdes Shelf in southern California (Stullet al., 1996; Zeng and Venkatesan, 1999; Lee andWiberg, 2002). In the early 1970s, California sea lions,Zalophus californianus, contained very high tissue levelsof DDT and PCBs (blubber levels of up to 2700 and145 mg/kg, respectively; Le Boeuf and Bonnell, 1971;DeLong et al., 1973). Since the cessation of DDTmanufacture in theUnited States and thedumping of its

* Corresponding author. Fax: C 32 10 473728.E-mail address: debier@bnut.ucl.ac.be (C. Debier).

0269-7491/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.doi:10.1016/j.envpol.2004.07.012

Environmental Pollution 134 (2005) 323–332www.elsevier.com/locate/envpol

PCB e tiroide in modelli animali

Riduzione degli ormoni circolanti anche in altri modelli animali

PCBs and DDT in the serum of juvenile California sea lions:associations with vitamins A and E and thyroid hormones

Cathy Debiera,* , Gina M . Ylitalob, M ichael Weisec, Frances Gullandd,Daniel P. Costac, Burney J. Le Boeufe, Tanguy de Tillessef, Yvan LarondelleaaUnite de Biochimie de la Nutrition, Universit e catholique de Louvain, Croix du Sud 2/8, B-1348 Louvain-la-Neuve, Belgium

bNOAA Fisheries/Environmental Conservation Division, 2725 Montlake Boulevard East Seattle, WA 98112, USAcDepartment of Ecology and Evolutionary Biology, Center for Ocean Health, 100 Shaffer Road, University of California,

Santa Cruz, CA 95060, USAdThe Marine Mammal Center, Marin Headlands, 1065 Fort Cronkhite, Sausalito, CA 94965, USAeOffice for Research, 401 Clark Kerr Hall, University of California, Santa Cruz, CA 95064, USA

fFaune & Biotopes, Allee de la Peupleraie, B-1300 Wavre, Belgium

Received 23 February 2004; accepted 26 July 2004

Results show high levels of organochlorine contaminants in juvenileCalifornia sea lions and a link between vitamin A, thyroid hormones and PCB exposure.

Abstract

Top-trophic predators like California sea lions bioaccumulate high levels of persistent fat-soluble pollutants that may provokephysiological impairments such as endocrine or vitamins A and E disruption. We measured circulating levels of polychlorinatedbiphenyls (PCBs) and dichlorodiphenyltrichloroethane (DDT) in 12 healthy juvenile California sea lions captured on Ano NuevoIsland, California, in 2002. We investigated the relationship between thecontamination by PCBsand DDT and thecirculating levelsof vitamins A and E and thyroid hormones (thyroxine, T4 and triiodothyronine, T3). Serum concentrations of total PCBs (

PPCBs)

and total DDT were 14G 9mg/kg and 28G 19 mg/kg lipid weight, respectively. PCB toxic equivalents (PPCB TEQs) were

320G 170 ng/kg lipid weight. Concentrations ofPPCBs and

PPCB TEQs in serum lipids were negatively correlated ( p ! 0.05)

with serum vitamin A and T3, potentially reflecting PCB-related toxicity. A slight but not significant negative correlation ( p ! 0.1)was observed between serum T4 and the levels of

PPCBs and

PPCB TEQs. Conversely, no relationship was evident between the

contaminant concentrations and vitamin E ( pO 0.1). As juvenile California sea lions are useful sentinels of coastal contamination,the high levels encountered in their serum is cause for concern about the ecosystem health of the area.Ó 2004 Elsevier Ltd. All rights reserved.

Keywords: California sea lion; PCBs; DDT; Vitamin; Thyroid hormone

1. Introduction

The marine ecosystem of California is highlycontaminated by organochlorine pollutants (OCs) likePCBs and DDT that have been historically discharged

to the Palos Verdes Shelf in southern California (Stullet al., 1996; Zeng and Venkatesan, 1999; Lee andWiberg, 2002). In the early 1970s, California sea lions,Zalophus californianus, contained very high tissue levelsof DDT and PCBs (blubber levels of up to 2700 and145 mg/kg, respectively; Le Boeuf and Bonnell, 1971;DeLong et al., 1973). Since the cessation of DDTmanufacture in theUnited States and thedumping of its

* Corresponding author. Fax: C 32 10 473728.E-mail address: debier@bnut.ucl.ac.be (C. Debier).

0269-7491/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.doi:10.1016/j.envpol.2004.07.012

Environmental Pollution 134 (2005) 323–332www.elsevier.com/locate/envpol

1096 Environ. Toxicol. Chem. 20, 2001 I. Chiba et al.

Fig. 1. Relationship of blubber polychlorinated biphenyls (PCB)180levels (on a fat-weight basis) and plasma total T3 levels in larga andribbon seals. Spearman rank correlation coefficients are shown.

and their metabolites as this study. These changes are thoughtto be caused by their interference with thyroid gland functionand morphology, thyroid hormone metabolism, and plasmatransport. Possible mechanisms underlying the negative cor-relation between total T3 and PCBs in ribbon seals could beas follows: inhibition of T4 deiodinase activity by PCBs [37]and interference with T3 binding to carrier proteins by PCBs[38]. As another mechanism, promotion of T3 metabolism bydeiodination, glucuronidation, or sulfation may also lead to aT3 decrease in seal plasma.

It is known that age affects the plasma thyroid hormonelevels. Hall et al. [15] pointed out that in gray seal pup pop-ulations, the effect of age on the serum thyroid hormone con-centration should be taken into account. Recent reports alsosupport this suggestion, particularly during lactation [20,39].In ribbon seals, relatively poor correlations were observedbetween plasma thyroid hormone concentrations and age (Ta-ble 2). In addition, molt in the same species may also affectthe plasma thyroid hormone level [19]. Animals used in thisstudy were not in the molt condition. Therefore, we do notconsider it likely that molt is a factor involved in thyroidhormone level in this study. Some reports suggested that sexfactors may affect the plasma thyroid hormone level [40]. Inthis study, in ribbon seals, no significant sex differences inplasma T3 (p 5 0.12) and T4 (p 5 0.35) levels were observed(Mann–Whitney U test). These results might be due to the lowsample size and the high variability within sexes.

The present study revealed that plasma T3 deficiency inribbon seals could be due to exposure to some CHCs, such ascoplanar PCB congeners and oxychlordane. Similar conclu-sions might have been obtained for T3 levels in larga seals ifthe sample size had been greater. However, much remains to

be done to clarify the link between the accumulation of CHCsand thyroid hormone modulation in free-ranging seal species.An understanding of the mechanistic base of the thyroid hor-mone system in these species would be helpful in unravelingpossible hormonal toxicity of CHCs.

Acknowledgement—We thank local fishermen in Raus and volunteersfor seal collection and Y. Shimamoto, S.J. Yoon, Y. Maruyama, Y.Tateishi, and Y. Maeda for valuable discussions. This study was sup-ported by grants-in-aid 09306021 and 09876084 from the Ministryof Education, Science and Culture of Japan, to H. Iwata.

REFERENCES1. Iwata H, Tanabe S, Sakai N, Tatsukawa R. 1993. Distribution of

persistent organochlorines in the oceanic air and surface seawaterand the role of ocean on their global transport and fate. EnvironSci Technol 27:1080–1098.

2. Muir DCG, Norstrom RJ, Simon M. 1988. Organochlorine con-taminants in arctic marine food chains: Accumulation of specificpolychlorinated biphenyls and chlordane-related compounds. En-viron Sci Technol 22:1071–1079.

3. Tanabe S, Watanabe S, Kan H, Tatsukawa R. 1988. Capacity andmode of PCB metabolism in small cetaceans. Mar Mamm Sci 4:103–124.

4. Tanabe S, Iwata H, Tatsukawa R. 1994. Global contamination bypersistent organochlorines and their ecotoxicological impact onmarine mammals. Sci Total Environ 154:163–177.

5. Reijinders PJH. 1986. Reproductive failure in common seals feed-ing on fish from polluted coastal waters. Nature 324:456–457.

6. Brouwer A, Reijinders PJH, Koeman JH. 1989. Polychlorinatedbiphenyl (PCB)-contaminated fish induces vitamin A and thyroidhormone deficiency in the common seal (Phoca vitul ina). AquatToxicol 15:99–106.

7. de Swart RL, et al. 1994. Impairment of immune function inharbor seals (Phoca vitul ina) feeding on fish from polluted waters.Ambio 23:155–159.

8. Ross PS, de Swart RL, Reijnders PJ, van Loveren H, Vos JG,Osterhaus ADME. 1995. Contaminant-related suppression of de-layed-type hypersensitivity and antibody responses in harbor sealsfed herring from the Baltic Sea. Environ Health Perspect 103:162–167.

9. de Swart RL, Ross PS, Vos JG, Osterhaus ADME. 1996. Impairedimmunity in harbour seals (Phoca vitul ina) exposed to bioac-cumulated environmental contaminants: Review of a long-termfeeding study. Environ Health Perspect 104:823–828.

10. Beckmen KB, Lowenstine LJ, Newman J, Hill J, Hanni K, GerberJ. 1997. Clinical and pathological characterization of northernelephant seal skin disease. J Wildl Dis 33:438–449.

11. Subramanian A, Tanabe S, Tatsukawa R, Saito S, Miyazaki N.1987. Reduction in the testosterone levels by PCBs and DDE inDall’s porpoises of northwestern North Pacific. Mar Pollut Bul l18:643–646.

12. Brouwer A, et al. 1995. Functional aspects of developmentaltoxicity of polyhalogenated aromatic hydrocarbons in experi-mental animals and human infants. Eur J Pharmacol 293:1–40.

13. Morse DC, Wehler EK, Wesseling W, Koeman JH, Brouwer A.1996. Alterations in rat brain thyroid hormone status followingpre- and postnatal exposure to polychlorinated biphenyls (Aro-clor1254). Toxicol Appl Pharmacol 136:269–279.

14. Jenssen BM, Skaare JU, Woldstad S, Nastad AT, Haugen O, Klov-en B, Sormo EG. 1995. Biomarkers in blood to assess effects ofpolychlorinated biphenyls in free-living grey seal pups. In BlixAS, Walloe L, Ulltang O, eds, Whales, Seals, Fish and Man:Developments in Mar ine Biology, Vol 4. Elsevier, Amsterdam,The Netherlands, pp 607–615.

15. Hall AJ, Green NJL, Jones KC, Pomeroy PP, Harwood J. 1998.Thyroid hormones as biomarkers in grey seals. Mar Pollut Bul l36:424–428.

16. Wakimoto T, Tatsukawa R, Ogawa T. 1971. Analytical methodof PCBs. J Environ Pol lut Control 7:517–522.

17. Tanabe S, Tanaka H, Tatsukawa R. 1984. Polychlorobiphenyls,tDDT, and hexachlorocyclohexane isomers in the western NorthPacific ecosystem. Arch Environ Contam Toxicol 13:731–738.

18. Van den Berg M, et al. 1998. Toxic equivalency factors (TEFs)

1092

Environmental Toxicology and Chemistry, Vol. 20, No. 5, pp. 1092–1097, 2001q 2001 SETAC

Printed in the USA0730-7268/01 $9.00 1 .00

NEGATIVE CORRELATION BETWEEN PLASMA THYROID HORMONE LEVELS ANDCHLORINATED HYDROCARBON LEVELS ACCUMULATED IN SEALS FROM THE

COAST OF HOKKAIDO, JAPAN

ISSEI CHIBA,† AKIHITO SAKAKIBARA,‡ YOKO GOTO,§ TAKEOMI ISONO,§ YUKIE YAMAMOTO,§ HISATO IWATA,†‡SHINSUKE TANABE,‡ KENJI SHIMAZAKI,§ FUMIAKI AKAHORI,zzAKIO KAZUSAKA,† and SHOICHI FUJITA*†

†Laboratory of Toxicology, Department of Environmental Veterinary Sciences, Graduate School of Veterinary Medicine,Hokkaido University, Kita-ward N18W9, Sapporo 060-0818, Japan

‡Center for Marine Environmental Studies, Ehime University, Tarumi 3-5-7, Matsuyama 790-8566, Japan§Division Marine Ecology, Research Institute of North Pacific Fishery, Faculty of Fisheries, Hokkaido University, Minatocho 3-1-1,

Hakodate 041-0821, JapanzzHigh-tech Research Center, Azabu University, Fuchinobe 1-17-71, Sagamihara 229-8501, Japan

(Received 1 Apr i l 2000; Accepted 29 September 2000)

Abstract—Chlorinated hydrocarbon (CHC) levels in the blubber of larga seals (Phoca largha) and ribbon seals (Phoca fasciata)collected from the coastal waters of Hokkaido, Japan, were determined in order to assess the hormonal effects of CHC exposurein free-ranging pinnipeds. Plasma thyroid hormone levels, including total thyroxine (T4), free thyroxine (free T4), total triiodo-thyronine (T3), and free triiodothyronine (free T3), were also measured. Higher concentrations of polychlorinated biphenyl congeners(PCBs), dichlorodiphenyltrichloroethane and its metabolites, and chlordane compounds were found in the range of 380 to 2,600ng/g, 350 to 2,600 ng/g, and 120 to 760 ng/g on a wet-weight basis, respectively. Spearman rank correlation analyses showed thatin larga seals, plasma total T3 and free T3 levels negatively correlated with levels of all the CHCs analyzed, although there wasno such correlation between total or free T4 levels and CHC concentrations. In ribbon seals, total T3 levels significantly decreasedwith an increase of di-ortho PCB (PCB170 and 180) residues. These findings indicated that the plasma T3 deficiency could beassociated with some CHC exposure in larga and ribbon seals and that the responses of plasma thyroid hormones may be usefulbiomarkers for CHC exposure in ribbon seals.

Keywords—Seal Thyroid hormone Chlorinated hydrocarbon

I NTRODUCT ION

Chlorinated hydrocarbons (CHCs) are ubiquitous contam-inants detected in the marine environment on a global scale[1] and are notably bioaccumulated into ecosystems throughthe food web [2,3]. Contamination of marine organisms byCHCs such as polychlorinated biphenyl congeners (PCBs) anddichlorodiphenyltrichloroethane (DDT) continues to be an is-sue of concern. Recent concerns are based on indications thatCHCs are major chemicals causing adverse effects, includingendocrine disruption, in higher trophic animals, such as marinemammals [4]. Some reports have shown reproductive impair-ment of marine mammal populations in some locally pollutedareas and suggested a link of marine pollution by bioaccu-mulative contaminants with die-offs [5].

Several field and experimental investigations have indicatedthat endocrine disruption is associated with hormonal modu-lation due to CHC exposure in marine mammals. Studies ofcaptive seals fed contaminated fish demonstrated that envi-ronmental contaminants induce plasma thyroid hormone andvitamin A deficiencies [6] as well as impairment of immunefunction [7–9]. Beckmen et al. [10] have pointed out that skin-diseased northern elephant seals in California have more de-pressed levels of thyroid and retinol and more elevated levelsof PCBs and p,p9-dichlorodiphenyldichloroethylene (p,p9-DDE) than unaffected seals. Subramanian et al. [11] showedthat plasma testosterone levels were significantly decreased

* To whom correspondence may be addressed(fujita@vetmed.hokudai.ac.jp).

with an increase in p,p9-DDE concentrations in the blubber ofDall’s porpoise from the northwestern North Pacific.

Among endocrine-disrupting effects, thyroid hormones areincreasingly used as sensitive biomarkers for studies of toxicresponses to chemical exposure. Thyroid hormones, namely3,5,39-triiodothyronine (T3) and 3,5,39,59-tetraiodothyronine(T4), have important roles in DNA transcription, differentia-tion of tissues, regulation of growth, and metabolic processes.Hypothyroidism leads to adverse effects such as a decreasedbasic metabolic rate, impairment of growth, and higher sen-sitivity to cold. It has been shown that maternal exposure toPCBs affects brain development of offspring through thyroidhormone deficiency in experimental animals [12,13].

Although a few studies have been done on the effects ofCHC exposure on thyroid hormone levels in free-ranging sealsover the last few years, little agreement still exists as to therelationship between the hormone and CHC levels [14,15].The major objective of this study is to provide more data onthe relationship between CHC exposure and thyroid hormonelevels in two seal species. We investigated whether plasmathyroid hormone levels could be altered by CHC exposure intwo free-ranging seal species, larga seals (Phoca largha) andribbon seals (Phoca fasciata), from the coast of Hokkaido,Japan. The present study also discusses the association of thethyroid hormone levels with age as a possible influential factor.

M ATERIALS AND M ETHODSSamples

Plasma, blubber, and canine tooth samples were collectedin 1997 from four larga seals (two male, two female) and 13

PCB e ormoni tiroidei nell’uomo

PBDE e tiroide: modelli animali

Developmental exposure to decabromodiphenyl ether (PBDE 209):Effects on thyroid hormone and hepatic enzyme activity in

male mouse offspring

Li-Ho Tseng a,b, Mei-Hui L i c, Shinn-Shyong Tsai d, Chia-Wei Lee a,M in-Hsiung Pan e, Wei-Jen Yao f, Ping-Chi Hsu a,*

a Department of Safety, Health and Environmental Engineering, National Kaohsiung First University of Science and Technology,No. 2, Jhuoyue Road, Nanzih District, Kaohsiung City 811, Taiwan

b Department of Occupational Safety and Hygiene, Tajen University, Pingtung, Taiwanc Environmental Toxicology Lab, Department of Geography, National Taiwan University, Taipei, Taiwan

d Department of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung, Taiwane Department of Seafood Science, National Kaohsiung Marine University, Kaohsiung, Taiwan

f Department of Nuclear Medicine, National Cheng Kung University Medical Center, Tainan, Taiwan

Received 2 May 2007; received in revised form 25 June 2007; accepted 28 June 2007Available online 14 August 2007

Abstract

Decabrominated diphenyl ether (PBDE 209) is the second most used brominated flame retardant (BFRs). Many studies have shownthat someof theBFRsact asendocrinedisruptors via alterations in thyroid hormonehomeostasis and affect development. L ittle isknownabout theeffect of prenatal exposure to PBDE 209 on thedevelopment in maleoffspring. Using a CD-1 mousemodel, weattempt to esti-mate thepossible effect of in utero exposure to PBDE 209 on thyroid hormone and hepatic enzymesactivities in male offspring. Pregnantmicewere administered different doses of PBDE 209 (10, 500, and 1500 mg/kg/day) or corn oil for controls per gavage from gestationaldays0–17. In adult maleoffspring whosemothers had been treated with 1500 mg/kg of PBD 209, hepatic enzymeactivity of S9 7-ethoxy-resorufin O-deethylase (EROD) wasweak but significantly increased (54%). However, no significant changeswereobserved in S9 4-nitro-phenol uridinediphosphate-glucuronosyltransferase (UDPGT) in any of the treatment groups. Serum triiodothyronine (T3) was found tohavedecreased significantly (ca. 21%both 10mg/kg and 1500mg/kg) in offspring, but not thyroxine (T4). Histopathological examinationrevealed that prenatal exposure of PBDE 209 might be related with cell swelling of hepatocytes in male offspring and there were mildchanges in the thyroid glands in 1500 mg/kg group. Thesedata demonstrate that PBDE 209 is likely an endocrine disrupter in malemicefollowing exposure during development. Further studies using environmentally relevant doses are needed for hazard identification.Ó 2007 Elsevier Ltd. All rights reserved.

Keywords: Decabrominated diphenyl ether (PBDE 209); Prenatal exposure; Thyroid hormone; Hepatic enzyme activity

1. Introduction

Polybrominated diphenyl ethers (PBDEs) are widelyused as additive flame retardants in our modern life.PBDEs could easily leach into the environment duringproducts are manufactured, used or disposed of (Sjodin

et al., 2001). PBDEs are also widely used in a variety ofconsumer products and can be found in food, householddust and sewage sludge worldwise. Moreover, severalregional studies have indicated time trend increases in con-centrations of these substances in humans (Akutsu et al.,2003; Schecter et al., 2005; Fangstrom et al., 2005) as wellas in the environment (Law et al., 2003).Decabromodiphenyl ether (PBDE 209) is the most

important commercially in both production and use ofPBDEs (WHO, 1994). Nowadays, PBDE 209 is mostly

0045-6535/$ - see front matter Ó 2007 Elsevier Ltd. All rights reserved.doi:10.1016/j.chemosphere.2007.06.078

* Corresponding author. Tel.: + 886 7 6011000x2322 (Off.)/+ 886 62131276 (Res.); fax: + 886 7 6011061.E-mail address: pchsu@ccms.nkfust.edu.tw (P.-C. Hsu).

www.elsevier.com/locate/chemosphere

Available online at www.sciencedirect.com

Chemosphere 70 (2008) 640–647

In conclusion, theresult of this studyfinds prenatalexposure to PBDE209 is able to reduceserum total T3concentrations inmale offspring .

Livelli di PBDE e funzione tiroidea in soggettiadulti

ConclusionThe results from our repeated measures cohort studysuggest that environmental exposure to PBDEs isassociated with reduced TT4 levels. The lack ofclear associations with other thyroid functionparameters suggests that the negative associationwith TT4 might be a consequence of decreasedserum binding of T4. This finding is consistent withthe toxicological literature and with some humanstudies. Our conclusions were robust to potentialconfounders and to various methods of data analysis.Prospective studies are needed to further understandhow PBDEs and their metabolites may affect THhomeostasis in healthy.

7

Figure S2A-B. Unadjusted cross-sectional associations between BDE-47 and Total T4 in Round 1: A)without outlier (N=46) B) with outlier (N=47)*.A)

B.

A) Relationship between BDE-47 and Total T4 in Round 1 without outlying participant (N=46) (β=-8.2, 95% CI: -12.3, -4.1). B) Relationship between BDE-47 and Total T4 in Round 1 with outlyingparticipant (N=47) (β=-2.7, 95% CI: -5.1, -0.27). * Outlying participant was a 64 year old, non-Hispanic white male.

Diossine e tiroide: modelli animali

• Riduzione della T4 totale e libera• Aumento del TSH• Iperplasia tiroidea

TT4

TT3

FT4

TSH

Diossine: effetti sui livelli di TSH neonatale

and coplanar PCBs (rs ¼ 0.82, p ¼ 0.001), whereas in thereference area no association was found with either plasmaTCDD (rs¼ 0.25; p¼ 0.51), or PCDD, PCDFs, and coplanarPCBs (rs¼ 0.11, p¼ 0.78).The analyses described above were based on plasma TCDD

levels that, for women with plasma TCDD . 10 ppt, wereextrapolated to the date of delivery using a first-orderpharmacokinetic model. Using the measured TCDD concen-trations in place of the extrapolated levels affected the resultsonly marginally. In particular, neonatal b-TSH levels ex-hibited significant associations in multivar iable models withplasma TCDD (b¼ 0.68, p¼ 0.002); plasma TEQs for PCDDs,PCDFs, and coplanar PCBs (b¼0.60, p¼0.004); and sum of alltotal TEQs (b¼ 0.65, p¼ 0.001).Asshown in Table 5, plasma dioxin levelswere significantly

higher in newbornswith b-TSH . 5 l U/ml. Plasma TCDD was

5.2 ppt (95% CI 4.1–6.7) in newborns with b-TSH 5 l U/mland 39.0 ppt (95% CI 8.9–173) in those with b-TSH . 5 l U/ml(p ¼ 0.005). Plasma TEQs for PCDDs, PCDFs, and coplanarPCBs were 30.6 ppt (95% CI 26.9–34.8) in newborns with b-TSH 5 l U/ml and 88.9 ppt (95% CI 43.1–183.5) in thosewith b-TSH . 5 l U/ml (p¼0.002). Also, in the group with b-TSH , 5 l U/ml non-coplanar PCBs levels (1.5 ppt, 95% CI1.2–1.8) and the sum of all TEQs (29.2 ppt, 95% CI 25.3–33.5)were significantly different from the levels found in the in thegroup with b-TSH 5 l U/ml (2.9 ppt, 95% CI 1.8–4.6, p¼0.003 for non-coplanar PCBs; 84.5 ppt, 95% CI 16.7–427.8, p¼0.01 for the sum of all TEQs).

Discussion

Neonatal b-TSH, which is used in most countr ies to screenfor congeni tal hypothyroidism, is considered a sensi tivemarker of subclinical pr imary hypothyroidism and a suitableindex of the presence of factors causing thyroid enlargementand potential alterations in function [1,29,30]. Our resultsfrom the Seveso populat ion showed that newborns ofmothers with high body burdens of TCDD, resulting fromaccidental dioxin exposure occurr ing approximately 20–30 yearlier, had higher neonatal b-TSH concentrations comparedto newborns of nonexposed women.In our residence-based population study, we observed ashift in the distr ibution of b-TSH toward higher levels in theexposed groups, thus suggesting that dioxin exposure mayproduce effects that are detectable at the population level.Mean b-TSH levels increased through the contaminationzones, with proportions of b-TSH . 5 l U/ml in the highlycontaminated areas (zones A and B) equivalent to thoseassociated with mild iodine deficiency (3%–19.9% accordingto the WHO) [1]. Epidemiological studies conducted in areaswith mild to moderate iodine deficiency have demonstrated,even in the absence of clinical hypothyroidism, abnormalitiesin psychoneuromotor and intellectual development, includ-ing impairment of visual-motor performances, motor skills,perceptual and neuromotor abilit ies, as well as reduceddevelopment and intellectual quotients (IQs) [29,31]. Post-natal cogni t ive and motor alterat ions have also beendescribed in children with perinatal exposure to dioxin-related compounds [10,32–36]. At the individual level, onlyeight of the newborns in our study had b-TSH levels . 10 l U/

Figure 1. Distribution of Neonatal b-TSH by Dioxin Contamination ZoneNeonatal b-TSH distribution for children born between 1994 and 2005 towomen from zone A (n¼54), the zonemost contaminated by TCDD afterthe Seveso accident; zone B (n ¼ 425); and the surrounding non-contaminated reference area (n¼ 533). The graph shows kernel densityestimates by zones.*According to the WHO [1], the percentage at the population level ofnewborns with a b-TSH value greater than 5 l U/ml should be less than3% in iodine-replete areas.doi:10.1371/journal.pmed.0050161.g001

Table 2. Neonatal b-TSH Levels in Children Born between 1994 and 2005 to Women from Zone A (the Zone Most Contaminated afterthe Seveso Accident), Zone B, and the Surrounding Noncontaminated Area (Reference)

Zone n Crude Multivariate Analysisa

Mean b-TSHb 95% CI p-Trendc Mean b-TSHb 95% CI p-Trendc

Reference 533 0.98 0.90–1.08 — 0.99 0.90–1.08 —B 425 1.35* 1.22–1.49 — 1.35* 1.23–1.50 —A 56 1.66* 1.19–2.31 , 0.001 1.63* 1.13–2.33 , 0.001

aEstimates from generalized estimating equations analysis adjusted for gender, birth weight, birth order, maternal age at delivery, hospital, and type of delivery.bStatistical analyses were performed on log-transformed b-TSH values to approximate normal distribution. Geometric b-TSH means and 95% CIs are reported.cRegression-based Wald-test for trend in b-TSH levels across the three zone categories performed by scoring the three zones based on plasma TCDD levels measured in femaleparticipants from the Seveso area (see Statistical Methods [17]).*p , 0.01 versus reference.doi:10.1371/journal.pmed.0050161.t002

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Dioxin and Neonatal Thyroid Function

and coplanar PCBs (rs ¼ 0.82, p ¼ 0.001), whereas in thereference area no association was found with either plasmaTCDD (rs¼ 0.25; p¼ 0.51), or PCDD, PCDFs, and coplanarPCBs (rs¼ 0.11, p¼ 0.78).The analyses described above were based on plasma TCDD

levels that, for women with plasma TCDD . 10 ppt, wereextrapolated to the date of delivery using a first-orderpharmacokinetic model. Using the measured TCDD concen-trations in place of the extrapolated levels affected the resultsonly marginally. In particular, neonatal b-TSH levels ex-hibited significant associations in multivar iable models withplasma TCDD (b¼ 0.68, p¼ 0.002); plasma TEQs for PCDDs,PCDFs, and coplanar PCBs (b¼0.60, p¼0.004); and sum of alltotal TEQs (b¼ 0.65, p¼ 0.001).Asshown in Table 5, plasma dioxin levelswere significantly

higher in newbornswith b-TSH . 5 l U/ml. Plasma TCDD was

5.2 ppt (95% CI 4.1–6.7) in newborns with b-TSH 5 l U/mland 39.0 ppt (95% CI 8.9–173) in those with b-TSH . 5 l U/ml(p ¼ 0.005). Plasma TEQs for PCDDs, PCDFs, and coplanarPCBs were 30.6 ppt (95% CI 26.9–34.8) in newborns with b-TSH 5 l U/ml and 88.9 ppt (95% CI 43.1–183.5) in thosewith b-TSH . 5 l U/ml (p¼0.002). Also, in the group with b-TSH , 5 l U/ml non-coplanar PCBs levels (1.5 ppt, 95% CI1.2–1.8) and the sum of all TEQs (29.2 ppt, 95% CI 25.3–33.5)were significantly different from the levels found in the in thegroup with b-TSH 5 l U/ml (2.9 ppt, 95% CI 1.8–4.6, p¼0.003 for non-coplanar PCBs; 84.5 ppt, 95% CI 16.7–427.8, p¼0.01 for the sum of all TEQs).

Discussion

Neonatal b-TSH, which is used in most countr ies to screenfor congeni tal hypothyroidism, is considered a sensi tivemarker of subclinical pr imary hypothyroidism and a suitableindex of the presence of factors causing thyroid enlargementand potential alterations in function [1,29,30]. Our resultsfrom the Seveso populat ion showed that newborns ofmothers with high body burdens of TCDD, resulting fromaccidental dioxin exposure occurr ing approximately 20–30 yearlier, had higher neonatal b-TSH concentrations comparedto newborns of nonexposed women.In our residence-based population study, we observed a

shift in the distr ibution of b-TSH toward higher levels in theexposed groups, thus suggesting that dioxin exposure mayproduce effects that are detectable at the population level.Mean b-TSH levels increased through the contaminationzones, with proportions of b-TSH . 5 l U/ml in the highlycontaminated areas (zones A and B) equivalent to thoseassociated with mild iodine deficiency (3%–19.9% accordingto the WHO) [1]. Epidemiological studies conducted in areaswith mild to moderate iodine deficiency have demonstrated,even in the absence of clinical hypothyroidism, abnormalitiesin psychoneuromotor and intellectual development, includ-ing impairment of visual-motor performances, motor skills,perceptual and neuromotor abilit ies, as well as reduceddevelopment and intellectual quotients (IQs) [29,31]. Post-natal cogni t ive and motor alterat ions have also beendescribed in children with perinatal exposure to dioxin-related compounds [10,32–36]. At the individual level, onlyeight of the newborns in our study had b-TSH levels . 10 l U/

Figure 1. Distribution of Neonatal b-TSH by Dioxin Contamination ZoneNeonatal b-TSH distribution for children born between 1994 and 2005 towomen from zone A (n¼54), the zonemost contaminated by TCDD afterthe Seveso accident; zone B (n ¼ 425); and the surrounding non-contaminated reference area (n¼ 533). The graph shows kernel densityestimates by zones.*According to the WHO [1], the percentage at the population level ofnewborns with a b-TSH value greater than 5 l U/ml should be less than3% in iodine-replete areas.doi:10.1371/journal.pmed.0050161.g001

Table 2. Neonatal b-TSH Levels in Children Born between 1994 and 2005 to Women from Zone A (the Zone Most Contaminated afterthe Seveso Accident), Zone B, and the Surrounding Noncontaminated Area (Reference)

Zone n Crude Multivariate Analysisa

Mean b-TSHb 95% CI p-Trendc Mean b-TSHb 95% CI p-Trendc

Reference 533 0.98 0.90–1.08 — 0.99 0.90–1.08 —B 425 1.35* 1.22–1.49 — 1.35* 1.23–1.50 —A 56 1.66* 1.19–2.31 , 0.001 1.63* 1.13–2.33 , 0.001

aEstimates from generalized estimating equations analysis adjusted for gender, birth weight, birth order, maternal age at delivery, hospital, and type of delivery.bStatistical analyses were performed on log-transformed b-TSH values to approximate normal distribution. Geometric b-TSH means and 95% CIs are reported.cRegression-based Wald-test for trend in b-TSH levels across the three zone categories performed by scoring the three zones based on plasma TCDD levels measured in femaleparticipants from the Seveso area (see Statistical Methods [17]).*p , 0.01 versus reference.doi:10.1371/journal.pmed.0050161.t002

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Dioxin and Neonatal Thyroid Function

Neonatal Thyroid Function in Seveso 25 Yearsafter Maternal Exposure to DioxinAndrea Baccarelli1,2,3*, Sara M. Giacomini2,3, Carlo Corbetta4, Maria Teresa Landi5, Matteo Bonzini2,3,Dario Consonni2,3, Paolo Grillo2,3, Donald G. Patterson Jr.6, Angela C. Pesatori2,3, Pier Alberto Bertazzi2,3

1 Department of Environmental Health, Harvard School of Public Health, Boston, Massachusetts, United States of America, 2 Department of Occupational and EnvironmentalHealth, Clinica del Lavoro ‘‘L. Devoto,’’ University of Milan, Milan, Italy, 3 Department of Preventive Medicine, Istituto di Ricovero e Cura a Carattere Scientifico (IRCCS)Ospedale Maggiore Policlinico, Mangiagalli, Regina Elena Foundation, Milan, Italy, 4 Neonatal Screening Laboratory, ‘‘V. Buzzi’’ Children’s Hospital, Milan, Italy, 5 GeneticEpidemiology Branch, Division of Cancer Epidemiology and Genetics, National Cancer Institute, National Institutes of Health/Department of Health and Human Services (NIH/DHHS), Bethesda, Maryland, United States of America, 6 EnviroSolutions Consulting, Jasper, Georgia, United States of America

Funding: This work was supportedby the following Research Grants:Italian Ministry of University andScientific Research (MIUR)Internationalization Program 2004–2006/97-C, and CARIPLO Foundationand Lombardy Region ResearchContracts numbers UniMi 8614/2006and UniMi 9167/2007. The studysponsors had no role in the studydesign; collection, analysis, andinterpretation of data; writing of thepaper; and decision to submit it forpublication.

Competing Interests: The authorshave declared that no competinginterests exist.

Academic Editor: Bruce Lanphear,University of Cincinnati, UnitedStates of America

Citation: Baccarelli A, Giacomini SM,Corbetta C, Landi MT, Bonzini M, etal. (2008) Neonatal thyroid functionin Seveso 25 years after maternalexposure to dioxin. PLoSMed 5(7):e161. doi:10.1371/journal.pmed.0050161

Received: December 17, 2007Accepted: June 17, 2008Published: July 29, 2008

Copyright : Ó 2008 Baccarelli et al.This is an open-access articledistributed under the terms of theCreative Commons AttributionLicense, which permits unrestricteduse, distribution, and reproductionin any medium, provided theoriginal author and source arecredited.

Abbreviations: b-TSH, bloodthyroid-stimulating hormone; CI,confidence interval; OR, odds ratio;PCB, polychlorinated biphenyl;PCDD, dibenzo-p-dioxin; PCDF,dibenzofuran; ppt, parts per trillion;TCDD, 2,3,7,8-Tetrachlorodibenzo-p-dioxin; TEQ, toxic equivalent; WHO,World Health Organization

* To whom correspondence shouldbe addressed. E-mail: abaccare@hsph.harvard.edu

A B ST R A C T

BackgroundNeonatal hypothyroidism has been associated in animal models with maternal exposure toseveral environmental contaminants; however, evidence for such an association in humans isinconsistent. We evaluated whether maternal exposure to 2,3,7,8-Tetrachlorodibenzo-p-dioxin(TCDD), a persistent and widespread toxic environmental contaminant, is associated withmodified neonatal thyroid function in a large, highly exposed population in Seveso, Italy.

Methods and FindingsBetween 1994 and 2005, in individuals exposed to TCDD after the 1976 Seveso accident weconducted: (i) a residence-based population study on 1,014 children born to the 1,772 womenof reproductive age in the most contaminated zones (A, very high contamination; B, highcontamination), and 1,772 age-matched women from the surrounding noncontaminated area(reference); (ii) a biomarker study on 51 mother–child pairs for whom recent maternal plasmadioxin measurements were available. Neonatal blood thyroid-stimulating hormone (b-TSH) wasmeasured on all children. We performed crude and multivariate analyses adjusting for gender,birth weight, birth order, maternal age, hospital, and type of delivery. Mean neonatal b-TSHwas0.98 l U/ml (95% confidence interval [CI] 0.90–1.08) in the reference area (n¼533), 1.35 l U/ml(95%CI 1.22–1.49) in zone B (n¼425), and 1.66 l U/ml (95%CI 1.19–2.31) in zone A (n¼56) (p, 0.001). The proportion of children with b-TSH . 5 l U/ml was 2.8% in the reference area,4.9% in zone B, and 16.1% in zone A (p , 0.001). Neonatal b-TSH was correlated with currentmaternal plasma TCDD (n¼51, b¼0.47, p , 0.001) and plasma toxic equivalents of coplanardioxin-like compounds (n¼ 51, b¼0.45, p¼ 0.005).

ConclusionsOur data indicate that environmental contaminants such as dioxins have a long-lastingcapability to modify neonatal thyroid function after the initial exposure.

The Editors’ Summary of this article follows the references.

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