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A multi-individual pharmacokinetic model framework for interpreting time trends of persistent chemicals in human populations: application to a postban situation.

Ritter R, Scheringer M, MacLeod M, Schenker U, Hungerb├╝hler K - Environ. Health Perspect. (2009)

Bottom Line: For this case, the framework quantitatively describes the relationships among the half-life for reduction of body burdens of POPs derived from CSTD, the half-life describing decline in daily intake, and the half-life of elimination from the human body.The full utility of these data has not been exploited so far.An efficient and informative monitoring strategy for banned POPs in humans would coordinate sampling of consistent sets of CSTD from young adults with total diet studies.

View Article: PubMed Central - PubMed

Affiliation: Safety and Environmental Technology Group, ETH Zurich, Zurich, Switzerland.

ABSTRACT

Background: Human milk and blood are monitored to detect time trends of persistent organic pollutants (POPs) in humans. It is current practice to use log-linear regression to fit time series of averaged cross-sectional biomonitoring data, here referred to as cross-sectional trend data (CSTD).

Objective: The goals of our study are to clarify the interpretation of half-lives derived from fitting exponential functions to declining CSTD and to provide a method of estimating human elimination half-lives from CSTD collected in a postban situation.

Methods: We developed a multi-individual pharmacokinetic model framework and present analytical solutions for a postban period. For this case, the framework quantitatively describes the relationships among the half-life for reduction of body burdens of POPs derived from CSTD, the half-life describing decline in daily intake, and the half-life of elimination from the human body.

Results: The half-life derived from exponential fitting of CSTD collected under postban conditions describes the exposure trend and is independent of human elimination kinetics. We use a case study of DDT (dichlorodiphenyltrichloroethane) to show that CSTD can be combined with exposure data obtained from total diet studies to estimate elimination kinetics of POPs for humans under background exposure conditions.

Conclusions: CSTD provide quantitative information about trends in human exposure and can be combined with exposure studies to estimate elimination kinetics. The full utility of these data has not been exploited so far. An efficient and informative monitoring strategy for banned POPs in humans would coordinate sampling of consistent sets of CSTD from young adults with total diet studies.

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Related in: MedlinePlus

Schematic overview of the model framework. (A) Background daily intake, I(t) (Equation 1). (B) Modeled LD (Equation 6), representing the time trend of single individuals, modeled CSTD (Equation 7), and modeled CSD as functions of time. (C) Modeled CSD from (B) shown as a function of age (Equation 9).
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f1-ehp-117-1280: Schematic overview of the model framework. (A) Background daily intake, I(t) (Equation 1). (B) Modeled LD (Equation 6), representing the time trend of single individuals, modeled CSTD (Equation 7), and modeled CSD as functions of time. (C) Modeled CSD from (B) shown as a function of age (Equation 9).

Mentions: where t (years) is time (starting at t0, where t0 = 0 in the following equations), and I0 is the intake (nanograms per person per day) at t0. This intake function is shown in Figure 1A. Other intake functions can also be used if the model is solved numerically [see Supplemental Material (doi:10.1289/ehp.0900648.S1)].


A multi-individual pharmacokinetic model framework for interpreting time trends of persistent chemicals in human populations: application to a postban situation.

Ritter R, Scheringer M, MacLeod M, Schenker U, Hungerb├╝hler K - Environ. Health Perspect. (2009)

Schematic overview of the model framework. (A) Background daily intake, I(t) (Equation 1). (B) Modeled LD (Equation 6), representing the time trend of single individuals, modeled CSTD (Equation 7), and modeled CSD as functions of time. (C) Modeled CSD from (B) shown as a function of age (Equation 9).
© Copyright Policy - public-domain
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2721873&req=5

f1-ehp-117-1280: Schematic overview of the model framework. (A) Background daily intake, I(t) (Equation 1). (B) Modeled LD (Equation 6), representing the time trend of single individuals, modeled CSTD (Equation 7), and modeled CSD as functions of time. (C) Modeled CSD from (B) shown as a function of age (Equation 9).
Mentions: where t (years) is time (starting at t0, where t0 = 0 in the following equations), and I0 is the intake (nanograms per person per day) at t0. This intake function is shown in Figure 1A. Other intake functions can also be used if the model is solved numerically [see Supplemental Material (doi:10.1289/ehp.0900648.S1)].

Bottom Line: For this case, the framework quantitatively describes the relationships among the half-life for reduction of body burdens of POPs derived from CSTD, the half-life describing decline in daily intake, and the half-life of elimination from the human body.The full utility of these data has not been exploited so far.An efficient and informative monitoring strategy for banned POPs in humans would coordinate sampling of consistent sets of CSTD from young adults with total diet studies.

View Article: PubMed Central - PubMed

Affiliation: Safety and Environmental Technology Group, ETH Zurich, Zurich, Switzerland.

ABSTRACT

Background: Human milk and blood are monitored to detect time trends of persistent organic pollutants (POPs) in humans. It is current practice to use log-linear regression to fit time series of averaged cross-sectional biomonitoring data, here referred to as cross-sectional trend data (CSTD).

Objective: The goals of our study are to clarify the interpretation of half-lives derived from fitting exponential functions to declining CSTD and to provide a method of estimating human elimination half-lives from CSTD collected in a postban situation.

Methods: We developed a multi-individual pharmacokinetic model framework and present analytical solutions for a postban period. For this case, the framework quantitatively describes the relationships among the half-life for reduction of body burdens of POPs derived from CSTD, the half-life describing decline in daily intake, and the half-life of elimination from the human body.

Results: The half-life derived from exponential fitting of CSTD collected under postban conditions describes the exposure trend and is independent of human elimination kinetics. We use a case study of DDT (dichlorodiphenyltrichloroethane) to show that CSTD can be combined with exposure data obtained from total diet studies to estimate elimination kinetics of POPs for humans under background exposure conditions.

Conclusions: CSTD provide quantitative information about trends in human exposure and can be combined with exposure studies to estimate elimination kinetics. The full utility of these data has not been exploited so far. An efficient and informative monitoring strategy for banned POPs in humans would coordinate sampling of consistent sets of CSTD from young adults with total diet studies.

Show MeSH
Related in: MedlinePlus