The Body's Burden

Toxicologists refer to the levels of xenobiotics (chemicals foreign to our metabolic pathways) in organs as “body burden”. It’s an interesting choice of words, when considering the meaning of burden as “that which is borne with difficulty”. The term has taken on considerable emotional significance for many people, with the growing awareness that we all are carrying around in our bodies the levels of a long list of chemical substances.

The Inside Bay Area (Oakland Tribune online) recently published a story of a family who volunteered for blood and urine sampling to analyze what’s in their body burdens. You hear the family’s concern now that they know what their exposures are, but don’t know the significance for their health, or what should be done about them, if anything. The paper presents the usual speculations about autism, asthma and infertility, which I have to set aside for the moment, and stick with what’s provable about these kinds of results: the nature and significance of health effects, if any, associated with the body burden is not known.

This is our "body burden" our chemical legacy, picked up from our possessions, passed to our children and sown across the environment. It's the result, scientists say, of 50 years of increasing reliance on synthetic chemicals for every facet of our daily lives.

Only recently have regulators grasped its scope. Health officials have yet to fully comprehend its consequence.

We are all, in a sense, subjects of an experiment, with no way to buy your way out, eat your way out or exercise your way out. We are guinea pigs when it comes to the unknown long-term threat these chemicals pose in our bodies and, in particular, our children.

That’s overly dramatic, and I differ from it in certain ways (I feel that the risks can be ranked even with limited information, and there are things under your control that can be done to reduce chemical exposure) but it’s not an unreasonable assessment of the situation. It’s a story well worth reading.

A more comprehensive picture of the body burden can be found in the Centers for Disease Control National Report on Human Exposure to Environmental Chemicals. These reports, released approximately every two years, present CDCs activities in monitoring human exposure to chemicals or their metabolites using biological monitoring (laboratory analysis of blood or urine samples). The Oakland Tribune essentially confirmed what this report states, which is that we are all carrying around trace levels of metals, plasticizers (phthalates), combustion products (polycyclic aromatic hydrocarbon metabolites and dioxins/furans), chlorinated hydrocarbon pesticides (DDT, hexachlorobenzene, lindane, chlordane, heptachlor epoxide), PCBs, organophosphorus insecticide metabolites, other pesticides (various herbicides, including atrazine, 2,4-D/2,4,5-T and pentachlorophenol), tobacco smoke indicators (cotinine) and phytoestrogens (the complete list examined in the CDC report is here).

The report offers the following, in order to encourage people not to take its findings out of proportion:

Just because people have an environmental chemical in their blood or urine does not mean that the chemical causes disease.

However, CDC does state that more research is needed to determine what adverse effects, if any, are associated with these body burdens.

One class of chemicals that CDC has not yet included in their survey, but will be in the future, are polybrominated diphenyl ethers (PBDEs). Very limited information from one study indicates that exposures of American mothers and infants to PBDEs may be higher than corresponding exposure to Swedish mothers and infants. Concentrations of PBDEs in adipose tissue and breast milk are reported to be increasing, in contrast to dioxins and PCB exposures, which have decreased over time (I’ll be writing later about the mounting concerns associated with PBDE exposures – until then, you can read more about them here and here).

Ever since seeing this study recently in the news regarding household dust as a potential exposure pathway for PBDEs, it seems that everyone has been getting into the act (here, here and here). It’s not just a stunt – there’s science behind it, if the data are collected properly.

The Inside Bay Area has an entire series of articles on chemical body burden, including an online exposure calculator, and most interesting to me, a story on how they did the study including a model study protocol. It’s not something you’ll want to run out and do any time soon – the cost for biological sampling (blood, urine and hair) and laboratory analysis for a family of four was around $17,000.

Postscript: tip of the hat to Environmental Health News for leading me to the Oakland Tribune article.