Main Challenges Related to Measuring Biomarkers of Exposure of Bisphenol A and Triclosan

Transcription

1 Main Challenges Related to Measuring Biomarkers of Exposure of Bisphenol A and Triclosan Antonia M. Calafat, PhD Organic Analytical Toxicology Branch Division of Laboratory Sciences National Center for Environmental Health Workshop on Bisphenol A, Triclosan and Parabens in HBM December 1, 2011 Brussels, Belgium National Center for Environmental Health Division of Laboratory Sciences

2 Biomonitoring Assessment of internal dose by measuring the parent chemical (or its metabolite or reaction product) in human specimens Integrates all sources/routes of exposure Trace concentrations (vs environmental levels) We measure concentrations, not exposures

3 Environmental Phenols Widely used industrial chemicals Triclosan Bisphenol A Endocrine disruptors (in-vitro and animal studies) Potential human effects are largely unknown Urinary conjugates as biomarkers of exposure Total (free + conjugates)

4 Exposure to BPA and Triclosan in U.S. Compound Age group (years) Geometric mean/95 th percentile urinary concentrations (µg/l) NHANES NHANES NHANES BPA / / / / / /13.2 Triclosan / / / / / /504 a N ~ 2600; representative population (6+ years ); spot sample

5 TCS concentration (µg/l) Triclosan Exposure Peak in 3 rd Decade: NHANES Calafat et al. EHP 2008, 116:303-7 Geometric mean Least square geometric mean Age group (years) Error bars indicate 95% confidence intervals

6 LSGM concentration (µg/l) Exposure to BPA: NHANES Detected in 92.6% of samples (N=2517) Calafat et al. EHP 2008, 116:39-44

7 What do BPA and TCS have in common? Variable concentrations (blood and urine) Non-persistent nature in body Episodic exposures Potential external contamination Ubiquitous in environment Biomarker is parent compound Sampling may affect concentrations Hospital/medical settings Calafat and Needham EHP 2009, 117:1481-5

8 Theoretical Post-Exposure Fate of Nonpersistent Chemical in Blood and Urine Blood Toxicant/Metabolite Urinary Metabolite Albumin Adduct DNA Adduct Hemoglobin Adduct If chemical forms adduct: extends time window of exposure Urinary Adduct Needham & Sexton. JEAEE 2000,10: Adapted from: Henderson et al. Crit Rev Toxicol 1989, 20: Time (Days)

9 BPA Dietary Exposure: Urine/Serum Concentrations 20 adults (controlled setting) Healthy, non-smokers, no dental work Housed for 24-h at clinical facility (2009) Ingested one of 3 specified meals of standard grocery store food items All voided urine collected at regular intervals over 24 h (N=389) Serum samples taken until 10 pm of study day (N=321) Urinary elimination (~1h time lag) correlated to serum time-course Variable [urine] and [serum] [Urine] av ~ 42*[serum] av Teeguarden et al. Toxicol Sci 2011, 123(1):48-57

10 Variability in Urinary Concentrations: BPA Example 8 adults: regular (uncontrolled) setting Collected all urine voids (N=427 including 56 FMV) for 7 days in 2005 Between-day/within-person variability: 77% (FMV) and 88% (24-h) of total variance Within-day variance (70%) > betweenperson (9%) and between-day/withinperson (21%) variances for spot collections Multiple collections per person to better categorize BPA exposure Time of collection and last urination Similar data for other NPPs [24-h] and [FMV] also variable Ye et al. EHP 2011, 119:983-8

11 Concentration (µg/g creatinine) Variability in Urinary Concentrations: Diet vs PCP Use 8 adults (7 days, all urine voids) MEP: between-person variability accounted for >75% of total variance MEHHP: within-person variability contributed 69 83% of total variance Similar BPA and MEHHP (DEHP) variability patterns Triclosan variability pattern likely to be similar to that of DEP/MEP Personal habits MEP MEHHP S1 S3 S5 S7 S2 S4 S6 S Preau et al. EHP 2010, 118(12): Day of week

12 Sampling Strategies (NPPs) Can a single sample adequately characterize an individual s average exposure for a given time period? For chronic exposures, probably For episodic exposures, maybe, depending upon type (e.g., diet, PCP use), frequency, and magnitude of exposure Time of collection and last urination for spot collections Age-related variability Can we overcome variability? Multiple urine collections per person Cost (storage, analysis) and compliance considerations Pooling several spot samples [NPPs] serum/plasma << [NPPs] urine Increased percentage of <LOD results?

13 LSGM urinary triclosan levels (µg/l) Despite Variability, Biomonitoring Data Still Show Exposure Differences: Case of Triclosan (NHANES ) Calafat et al. EHP 2008, 116:303-7 Household income

14 Consumption of canned soup vs soup prepared from fresh ingredients can increase exposure to BPA N = 75 persons Carwile et al. JAMA :

15 % Conjugated species Stability of Urinary Conjugates Room temperature storage TCS TCS and BPA excreted in urine mainly as conjugates Room temp, 4ºC and -70ºC Concentrations measured using on-line SPE-HPLC-MS/MS [Conc] conjugates = [Conc] total [Conc] free Urinary conjugates stable at -70ºC for years, but only a few days at room temperature Total concentrations stable BPA day 0 day 1 day 2 day 3 day 4 day 7 day 0 day 1 day 2 day 3 day 4 day 7 0 Ye et al. JESEE 2007, 17:

16 Serum Conjugates Compound Detection frequency (%) Mean (µg/l) Median (µg/l) Range (µg/l) BPA free 7 <0.3 <0.3 < BPA total 7 <0.3 <0.3 < MePb free < MePb total PrPb free <0.2 < PrPb total < Triclosan free 0 <1.1 <1.1 <1.1 Triclosan total <1.1 < Mean Conjugate ( %) ~100 N=15 adults (commercial samples; unknown collection procedures) Ye et al. Talanta 2008, 76:865-71

17 110 Stability of Conjugated Species of Phenols in Serum 16 commercial sera collected between 1998 and 2003 (Tennessee Blood Services, Memphis, TN, USA) In serum, conjugates (N=9/16) are stable for at least 30 days both at 25ºC and 37ºC BPA was not detected in any specimens 25ºC 37ºC Day 0 Day 5 Day 12 Day Day 0 Day 5 Day 12 Day M-Pb P-Pb TRCS 25-DCP 50 M-Pb P-Pb TRCS 25-DCP LOD=0.3 ng/ml (BPA), 1.1 ng/ml (TCS) Ye et al. Env Int 2009, 35:

18 Phenols in Human Milk Compound A B C D MePb free <LOD <LOD MePb total PrPb free <LOD <LOD 0.3 <LOD PrPb total <LOD <LOD 0.3 <LOD TCS free 2.8 <LOD 13.8 <LOD TCS total 3.4 <LOD 14.5 <LOD BPA free BPA total BP-3 free <LOD 1.2 <LOD <LOD BP-3 total <LOD 1.3 <LOD <LOD Ye et al. Anal. Chim. Acta 2008, 622:150-6 Concentrations in µg/l

19 Conjugates vs Free Species NPPs conjugates appear to be major species in urine and serum, but not in milk In urine, using total concentrations is adequate even when conjugates might have degraded Relative instability of conjugates at above freezing temperatures In serum, conjugates appear to be more stable than in urine Interpret trace levels of free species with caution because of potential for contamination (serum and urine) or degradation (urine)

20 Collection Protocols and Data Interpretation Collection in clinical settings Medical devices, IVs, and/or catheters Births, surgeries, other Plasticizers (e.g., DEHP, BPA) can leach from tubing [DEHP metabolites] >> [DEHP metabolites] background levels [BPA] >> [BPA] background levels [Other phthalate metabolites] unremarkable Biomonitoring data reflect true exposure, but may not reflect general environmental exposures Yan X et al. Hum Ecol Risk Assess 2009,15:565 78; Vandentorren et al. Environ Res 2011,111:761-4

21 External Contamination? Biomonitoring integrates all sources/routes of exposure Unknown contribution from external contamination Contamination before analysis Unknown sources/routes of exposure Ubiquitous chemical and trace levels in humans Collection procedure may be source Archived specimens We can t completely rule out external contamination Consistent use of field blanks and blind QCs Describe collection setting and sampling procedures Calafat and Needham EHP 2009, 117:1481-5

22 Final Thoughts Biomonitoring is one useful approach for exposure assessment Integrates sources/routes of exposure Many analytes can be measured, but not all analytes are good exposure biomarkers Interpretation of biomonitoring data Selection of appropriate biomarkers and matrix Multiple samplings may be needed (NPPs) Collection and handling considerations (how/when/where?) Stability Ubiquitous and unknown potential contamination sources Archived specimens and field blanks Good biomonitoring data improve exposure assessment

23 ACKNOWLEDGEMENTS

24 THANK YOU! For more information please contact Centers for Disease Control and Prevention 1600 Clifton Road NE, Atlanta, GA Telephone, CDC-INFO ( )/TTY: Web: The findings and conclusions in this report are those of the authors and do not necessarily represent the official position of the Centers for Disease Control and Prevention. National Center for Environmental Health Division of Laboratory Sciences