This is a discussion board prompt for Blackboard or Moodle covering the differences between primary and secondary source articles, relating concepts in lectures on the basics of biology to the environmental contaminant body burdens of humans. Students are asked to read a primary source article about the effect of mixtures of environmental contaminants and a secondary source article by National Geographic on the chemicals found in an average human body. Questions for the students range from: "For what audience is each article intended?" to "How do the concepts in each article link to the concepts in chapters 1 and 2?" Note: Buyers will need to be able to obtain the primary source article in Environ. Toxicol. Chem. 2012.