title: Understanding differences in the body burden-age relationships of bioaccumulating contaminants based on population cross sections versus individuals.
abstract: BACKGROUND
  Body burdens of persistent bioaccumulative contaminants estimated from the cross-sectional biomonitoring of human populations are often plotted against age. Such relationships have previously been assumed to reflect the role of age in bioaccumulation.
  
  
  OBJECTIVE
  We used a mechanistic modeling approach to reproduce concentration-versus-age relationships and investigate factors that influence them.
  
  
  METHODS
  CoZMoMAN is an environmental fate and human food chain bioaccumulation model that estimates time trends in human body burdens in response to time-variant environmental emissions. Trends of polychlorinated biphenyl (PCB) congener 153 concentrations versus age for population cross sections were estimated using simulated longitudinal data for individual women born at different times. The model was also used to probe the influence of partitioning and degradation properties, length of emissions, and model assumptions regarding lipid content and liver metabolism on concentration-age trends of bioaccumulative and persistent contaminants.
  
  
  RESULTS
  Body burden-age relationships for population cross sections and individuals over time are not equivalent. The time lapse between the peak in emissions and sample collection for biomonitoring is the most influential factor controlling the shape of concentration-age trends for chemicals with human metabolic half-lives longer than 1 year. Differences in observed concentration-age trends for PCBs and polybrominated diphenyl ethers are consistent with differences in emission time trends and human metabolic half-lives.
  
  
  CONCLUSIONS
  Bioaccumulation does not monotonically increase with age. Our model suggests that the main predictors of cross-sectional body burden trends with age are the amount of time elapsed after peak emissions and the human metabolic and environmental degradation rates.
authors.affiliation: Department of Chemistry, University of Toronto Scarborough, Toronto, Ontario, Canada.
authors.forename: Cristina L
authors.initials: CL
authors.lastname: Quinn
authors.forename: Frank
authors.initials: F
authors.lastname: Wania
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D001822:Body Burden; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D004781:Environmental Exposure; D004784:Environmental Monitoring; D004785:Environmental Pollutants / Q000032:analysis / Q000378:metabolism*; D005260:Female; D020387:Food Chain; D006207:Half-Life; D055768:Halogenated Diphenyl Ethers / Q000032:analysis / Q000378:metabolism*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008137:Longitudinal Studies; D008875:Middle Aged; D008956:Models, Chemical; D011078:Polychlorinated Biphenyls / Q000032:analysis / Q000378:metabolism*; D012680:Sensitivity and Specificity; D013997:Time Factors; D055815:Young Adult
chemical_list: D004785:Environmental Pollutants; D055768:Halogenated Diphenyl Ethers; D011078:Polychlorinated Biphenyls