Questions and Answers on Cord Blood Biomonitoring
Medical and Health Questions
1. What is “cord blood”?
2. Is cord blood the same as the mother’s blood?
3. How do chemicals get into cord blood? Doesn’t the placenta act as a barrier?
4. When is cord blood usually sampled?
5. What types of substances would be expected to be found in cord blood?
6. Why are environmental chemicals found in cord blood?
7. What do studies of cord blood tell us about prenatal exposures?
8. What is the medical significance of finding environmental chemicals in cord blood?
9. Should cord blood biomonitoring information be provided to the parents of the baby from which the sample was collected?
10. What does cord blood biomonitoring information mean to the baby's parents?
11. Is the baby during pregnancy at greater risk than newborns or children from exposures to even small amounts of chemicals?
12. Does the new information on chemicals in cord blood mean that babies and children are experiencing more exposures and at higher levels than in the past?
13. Some of the chemicals found in cord blood have been linked to cancer, birth defects, and other problems in laboratory animals. Does that mean that the baby is at risk?
14. Should a mother have her cord blood tested for substances?
15. Would it be prudent for women who are pregnant or trying to become pregnant to change their behavior based on the results of studies showing chemicals in cord blood?
Science and Regulatory Policy Questions
16. If EPA or FDA sets a safe exposure level for a substance for women, will that protect the developing baby as well?
17. Is there any way to compare cord blood levels to a reference standard to evaluate safety or degree of risk (includes explanation of Biomonitoring Equivalents)?
18. Should any chemical substance detected in cord blood be banned?
Other Questions
19. Are there ethical issues around sampling cord blood?
20. What about the anesthetics used in epidurals? Those are chemicals. Do they get into the fetal circulation, and are there any risks to the newborn?
21. Some reports claim that there is very little information available on the chemicals that are detected in cord blood. Is that a concern?
22. Does CDC include cord blood measurements in its National Exposure survey?
“Cord blood” is the blood in the baby’s umbilical cord. The umbilical cord’s function is to carry oxygen and nutrients to the baby and carry waste away.
2. Is cord blood the same as the mother’s blood?
Cord blood is not the same as the mother’s blood, but it is the same as the baby’s blood. One end of the umbilical cord is connected to the baby and the other to the placenta, an organ attached to the mother’s uterus. The placenta transports nutrients and waste products between the mother and the baby. The concentration of an environmental chemical in the mother’s blood may or may not be the same as that in the cord blood or in the baby.
3. How do chemicals get into cord blood? Doesn’t the placenta act as a barrier?
The placenta acts as an organ of exchange, allowing passage of nutrients to the baby and waste products out. The placenta also allows the passage of certain of the mother’s antibodies -- relatively large molecules compared to most environmental chemicals -- which are required to protect the baby from infection. Consequently, the placenta does not act as a complete barrier to any substance, natural or manmade, that an expectant mother is exposed to via food, water, air or anything she touches.
Because the placenta acts as an organ of exchange, not as a barrier, mothers-to-be are advised to watch their diets, avoid alcohol and cigarettes, and consult a doctor before taking medication, even over-the-counter medicines.
4. When is cord blood usually sampled?
Cord blood is normally obtained from the newborn’s umbilical cord, usually the umbilical vein. Blood from the umbilical cord is typically collected immediately after the baby is delivered and after the cord is clamped and/or cut. (See References 1, 2, 3)
5. What types of substances would be expected to be found in cord blood?
People are part of the environment, and our bodies absorb both natural and manmade substances in the environment through eating, breathing, and skin contact. We would expect to see many of the same chemicals that the mother is exposed to in the cord blood as well. This is why doctors and government agencies caution pregnant women on such things as the use of medications, consumption of alcohol, smoking, and eating foods with high levels of mercury. (See References 4)
6. Why are environmental chemicals found in cord blood?
Using the advanced analytical chemistry technologies available today, almost any substance, whether natural or manmade, can be detected in the environment and in human blood. In the past, chemistry methods were considered state-of-the-art if they could detect one part per million (the time equivalent of one second in 12 days (See References 5)). Now, with advanced analytical methods we often can detect one part per billion (one second in 32 years), one part per trillion (one second in 32 thousand years), or even one part per quadrillion (one second in 32 million years), depending on the specific chemical substances.
7. What do studies of cord blood tell us about prenatal exposures?
Measurements of environmental chemicals in cord blood are used to estimate prenatal exposures to natural and synthetic substances. Cord blood provides a snapshot of prenatal exposure at the end of pregnancy, but additional research is needed to evaluate whether this one-time measurement is of value as an indicator of exposure of the developing baby over the nine months in the womb. Moreover, cord blood measurements provide no information about sources or duration of exposure.
8. What is the medical significance of finding environmental chemicals in cord blood?
Biomonitoring provides descriptive information regarding the levels of chemicals found in the cord blood sample at the time of birth. Whether this information is of medical significance is an open question for the vast majority of chemicals, especially at levels representative of background exposure in the general population. As the Centers for Disease Control and Prevention (CDC), the U.S. public health research organization that conducts the national biomonitoring program, has said, “The measurement of an environmental chemical in a person’s blood or urine does not by itself mean that the chemical causes disease.” (See References 6)
9. Should cord blood biomonitoring information be provided to the parents of the baby from which the sample was collected?
There are divergent opinions on this issue among investigators, ethics committees and others. For the vast majority of chemicals that can be measured, there are no known health risks in humans that would prompt medical attention or intervention. Moreover, for the majority of chemicals there are no accepted or approved intervention strategies to reduce the concentration of a chemical in the body. Consequently, there is an important question of medical ethics here: how do you balance a parent’s desire for information about their baby with the potential anxiety that may arise from having information that may be of no known medical significance? This is an ethical issue that has been raised in the area of genetic screening and is also relevant for cord blood biomonitoring. (See References 7,8)
10. What does cord blood biomonitoring information mean to the baby’s parents?
If their baby’s cord blood biomonitoring information is provided to the parents, it is important to inform the parents that:
1) This is a snapshot measurement and it is unclear to what extent the measurement reflects exposure prior to birth
2) The information provides no information about sources of the mother’s exposure, and
3) The presence of a chemical does not necessarily mean that it has caused a health risk or disease.
Without this perspective, the information provided to parents may cause confusion and unnecessary anxiety. (See References 9)
11. Is the baby during pregnancy at greater risk than newborns or children from exposures to even small amounts of chemicals?
In some cases the developing baby may be more sensitive, and in other cases less sensitive. The concept of “windows of vulnerability” during fetal development and sexual maturation has been incorporated into research, testing, and chemical safety assessments for more than 40 years. For instance, standard laboratory animal studies involving testing for fetal and neonatal development. Multi-generation laboratory animal studies test for all possible sensitive live stages.
12. Does the new information on chemicals in cord blood mean that babies and children are experiencing more exposures and at higher levels than in the past?
More chemicals are being detected because technological advances in chemistry allow scientists to detect lower and lower concentrations of a larger array of substances. This has resulted in the detection of more chemicals, but at very low levels, commonly one part per billion or less.(See References 10) Data collected by the Centers for Disease Control and Prevention (CDC), the U.S. public health research organization that conducts the national biomonitoring program, show that levels of many substances of interest—dioxins, PCBs, DDT, lead, and mercury—have been declining over time. (See References 11,12)
13. Some of the chemicals found in cord blood have been linked to cancer, birth defects, and other problems in laboratory animals. Does that mean that the baby is at risk?
The detection of a chemical is not sufficient to determine risk. The dose also matters. All environmental substances, natural and manmade, have hazard properties that can be assessed in laboratory animal studies if the dose or exposure concentration is sufficiently high. This is even true for everyday substances like table salt or the dozens of ingredients in a multi-vitamin tablet. At a high enough dose, they too can elicit a toxic response. (See References 13)
14. Should a mother have her cord blood tested for substances?
Such testing is not routinely available and is very costly. If a mother has specific questions or concerns, she should consult her doctor.
15. Would it be prudent for women who are pregnant or trying to become pregnant to change their behavior based on the results of studies showing chemicals in cord blood?
Neither the Centers for Disease Control and Prevention (CDC), the U.S. public health research organization that conducts the national biomonitoring program, nor the National Research Council (NRC) of the U.S. National Academies of Science, which recently assessed the available science on biomonitoring, recommend any changes in behavior based on the presence of an environmental chemical in the body. (See References 14,15) Both have said that the presence of an environmental chemical in the body does not indicate that it causes a health risk or disease.
Studies showing environmental chemicals in the body do not provide information on possible sources of exposure or guidance on reducing exposures.
For the views of a medical doctor who is an expert on the presence of chemicals in the body, see “A Medical Doctor’s Perspective on Biomonitoring” at the BiomonitoringInfo.org website (http://www.biomonitoringinfo.org/mckay.html).
Science and Regulatory Policy Questions
16. If EPA or FDA sets a safe exposure level for a substance for women, will that protect the baby during pregnancy as well?
The processes used to set safe exposure levels account for possible exposure to the baby during pregnancy. The safety assessment process utilizes laboratory animal studies that measure for possible effects during reproduction and development. Safe exposure levels are based on exposure levels at which no harmful effects are observed in laboratory animal studies, the no observed adverse effect level (NOAEL). Safety factors of 100-fold or more are then used to account for the possible greater sensitivity of humans compared to laboratory animals and to account for sensitive subpopulations, such as babies during pregnancy. Safe exposure levels are then set at exposure levels 100-fold (or more) lower than the NOAEL. EPA refers to these safe exposure levels as “reference values.” EPA characterizes these as the levels at which exposures are likely to be without an appreciable risk of adverse health effects over a lifetime, including potentially sensitive developmental stages such as pregnancy. (See References 16)
17. Is there any way to compare cord blood levels to a reference standard to evaluate safety or degree of risk?
To date, scientists and medical professionals are able to provide such comparisons only for a few substances, such as lead and mercury, for which there are adequate data to compare blood levels to a reference value or safe exposure level. Academic, government and industry scientists are conducting considerable additional research on specific chemicals and on methods for comparing blood levels with safe exposure levels from laboratory animal studies. (See References 17)
18. Should a chemical substance detected in cord blood be banned?
Neither the Centers for Disease Control and Prevention (CDC), the U.S. public health research organization that conducts the national biomonitoring program, nor the National Research Council (NRC) of the National Academies of Science, which recently assessed the available science on biomonitoring, recommends restrictions based on the presence of an environmental chemical in the body. (See References 18, 19)
The CDC in their most recent National Report on Human Exposure to Environmental Chemicals said:
“Just because people have an environmental chemical in their blood or urine does not mean that the chemical causes disease. The toxicity of a chemical is related to its dose or concentration in addition to a person’s individual susceptibility. Small amounts may be of no health consequence, whereas larger amounts may cause adverse health effects. Research studies, separate from the report, are required to determine which levels of a chemical may cause health effects and which level are not a significant health concern.” (See References 20)
This assessment was affirmed by the NRC which said:
“As CDC states in its national-exposure reports, the findings of a chemical in people’s blood or urine does not necessarily mean that it causes a health risk or disease.” (See References 21)
19. Are there ethical issues around sampling cord blood?
Any program to sample cord blood must take the welfare of the child and mother into account as the primary concern. Thus, cord blood biomonitoring programs should be approved by independent Institutional Review Boards (IRB) to examine the study protocol for ethical and legal issues, and in so doing ensure the rights, well-being, and safety of the child and mother. An important protocol issue is posed by the ethical dilemma of the study subjects’ rights to their own data and the reporting of study results either as individual specific data or aggregate data. This issue needs to be discussed with the IRB prior to the start of any study and all subjects informed of the procedures for reporting of study results before they consent to participate.
20. What about the anesthetics used in epidurals? Those are chemicals. Do they get into the fetal circulation, and are there any risks to the newborn?
This is a good example of the fact that the presence of a chemical in the body does not necessarily indicate a health risk. The anesthetics in epidurals are chemicals, and they do get into the fetal circulation. However, potential risks are controlled by dose and timing. (See References 22)
21. Some reports claim that there is very little information available on the chemicals that are detected in cord blood. Is that a concern?
Considerable information is available on the health properties of environmental chemicals. For instance:
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The Agency for Toxic Substances and Disease Control (ATSDR) provides compendiums of the health information on a large number of substances.
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The U.S. EPA conducts research on environmental substances and has numerous sources of information available to the public.
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The EPA and the international Organization for Economic Cooperation and Development (OECD) compile and assess health and environmental information on high production volume (HPV) chemicals. (See References 23)
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The U.S. National Toxicology Program conducts research on possible health effects of chemical substances.
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The National Institute for Environmental Health Sciences provides grants to academic researchers for studies on environmental substances.
Academic, government and industry scientists are conducting new research to facilitate comparison of the levels of environmental substances in the body to the safe exposure levels determined from laboratory animal studies. Government agencies in the U.S. and Canada are actively supporting research in this area.
22. Does the Centers for Disease Control and Prevention (CDC) include cord blood measurements in its National Exposure survey?
Collection of cord blood samples requires a well equipped research hospital to collect the samples in a way that does not pose a risk to the newborn. The CDC uses Mobile Examination Centers, rather than hospitals, and has a policy of only collecting blood samples from individuals over the age of six, both of which currently preclude CDC from collecting cord blood samples. (See References 24)
These limitations suggest that cord blood sampling may not be suitable for, or may be very difficult to apply to the type of nationally representative sampling conducted by the CDC under the national biomonitoring program. Use of a nationally representative sample allows the CDC to assess levels of chemicals in the body for the entire US population.
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Perry, J., and Jagger, J. 2004. Collecting umbilical cord blood. Nursing. 34(10):20.
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Belles-Isles, M., Ayotte, P., Dewailly, É., Weber, J.P., Roy, R. 2002. Cord blood lymphocyte functions in newborns from a remote maritime population exposed to organochlorines and methylmercury. Journal of Toxicology and Environmental Health A. 65:165-182.
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Ramirez, G.B., Cruz, M.C., Pagulayan, O., Ostrea, E., Dalisay, C. 2000. The Tagum study I: Analysis and clinical correlates of mercury in maternal and cord blood, breast milk, meconium, and infants' hair. Pediatrics 106(4):774-781.
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See the discussion of lead and mercury levels in the commentary by Drs. C.A. McKay and J. H. Delgado on the BiomonitoringInfo.org website: http://www.biomonitoringinfo.org/new/20051128.html.
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One million seconds = 16,700 minutes = 278 hours = 11.6 days.
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Centers for Disease Control and Prevention (CDC), Third National Report on Human Exposure to Environmental Chemicals, 2005, Executive Summary, section on Interpreting the Data. http://www.cdc.gov/exposurereport/.
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Renegar, G. et al. 2006. Returning genetic research results to individuals: points-to-consider. Bioethics 20(1):24-36.
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Kuehn, B.M. 2008. Prenatal genome testing sparks debate. Journal of the American Medical Association 300(14):1637-1639.
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For one consideration of how lack of information or poor understanding of the medical benefits of medical research can lead to unethical manipulation of study participants, see Jansen, L.A. 2006. The problem with optimism in clinical trials. IRB: Ethics and Human Research. July-August: 13-19.
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Centers for Disease Control and Prevention (CDC), Third National Report on Human Exposure to Environmental Chemicals, 2005. Note units used in Executive Summary to report results for organic (non-metal) compounds: ng/L (parts per billion) for PAHs, fg/g (part per quadrillion) for dioxins/furans/coplanar PCBs, ng/g (parts per billion) for other PCBs, µg/L (parts per billion) for phthalates, and ng/g or µg/L (parts per billion) for pesticides/herbicides.
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Centers for Disease Control and Prevention (CDC). 2005. Third National Report on Human Exposure to Environmental Chemicals. http://www.cdc.gov/exposurereport/.
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See the discussion of lead and mercury levels in the commentary by Drs. C.A. McKay and J. H. Delgado on the BiomonitoringInfo.org website: http://www.biomonitoringinfo.org/new/20051128.html.
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Claims that chemicals cause cancer or other problems need to be put in context. In order to know the potential hazards of a chemical, researchers have to conduct laboratory animal studies using very high doses of chemicals. These doses are typically hundreds, thousands or tens of thousands of times higher than levels to which humans would ever be exposed. Lower doses expected in everyday life are used as well. As the dose of the substance is reduced, the hazard properties diminish until a “no-effect” dose is reached. This no observed effect level from animal studies is used to determine a safe exposure level for humans, often called a reference value, or reference dose, or tolerable daily intake.
This process uses health protective procedures in order to assure that the standards set for safe exposures to humans protect all individuals – adults, women of child bearing age, the developing baby, and children. For example, EPA Reference Values for chemicals are “An estimate of an exposure for a given duration to the human population (including susceptible subgroups) that is likely to be without an appreciable risk of adverse health effects over a lifetime” (http://www.epa.gov/iris/help_gloss.htm). EPA Reference Values are not set to zero; they are set at levels of exposure that are safe.
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Centers for Disease Control and Prevention (CDC). 2005. Third National Report on Human Exposure to Environmental Chemicals, Executive Summary, “Interpreting the Data.” http://www.cdc.gov/exposurereport/.
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National Research Council. 2006. Human Biomonitoring for Environmental Chemicals, p. 12.
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http://www.epa.gov/iris/help_gloss.htm
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H.J. Clewell, Y.M. Tan, J.L. Campbell and M.E. Andersen, Quantitative Interpretation of Human Biomonitoring Data, Toxicology and Applied Pharmacology, vol. 231, pp. 122-133, 2008;
Regulatory Toxicology and Pharmacology, vol. 51, number 3, supplement 1, Biomonitoring Equivalents: Guidelines and Case Studies, pp. S1-S77, 2008;
L.L. Aylward, J.S. LaKind and S.M. Hays, Derivation of Biomonitoring Equivalent (BE) Values for 2,3,7,8-Tetrachlorodibenzo-p-Dioxin (TCDD) and Related Compounds: A Screening Tool for Interpretation of Biomonitoring Data in a Risk Assessment Context, Journal of Toxicology and Environmental Health, Part A, vol. 71, pp. 1499-1508, 2008.
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Centers for Disease Control and Prevention (CDC). 2005. Third National Report on Human Exposure to Environmental Chemicals, Executive Summary, “Interpreting the Data.” http://www.cdc.gov/exposurereport/.
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National Research Council. 2006. Human Biomonitoring for Environmental Chemicals, p. 12.
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Centers for Disease Control and Prevention (CDC). 2005. Third National Report on Human Exposure to Environmental Chemicals, Executive Summary, “Interpreting the Data.” http://www.cdc.gov/exposurereport/.
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National Research Council. 2006. Human Biomonitoring for Environmental Chemicals, , p. 12.
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B.L. Leighton and S.H. Halpern. 2002. The effects of epidural analgesia on labor, maternal, and neonatal outcomes: A systematic review, American Journal of Obstetrics and Gynecology 186(5 part 2):S69-S77.
See also:
WebMD: http://www.webmd.com/baby/should-i-use-epidural-anesthesia-during-childbirth
Article by Researchers at Harvard School of Medicine: http://www.csaol.cn/img/2007pdf/b489.pdf
From a parenting website: http://www.transitiontoparenthood.com/ttp/parented/pain/epiduralfx.htm
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The information provided as part of EPA’s and OECD’s HPV assessment program include:
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identification and definition of possible hazards to all major organ systems from both acute and repeated exposures;
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detection of potential hazards arising from in utero exposures (developmental effects);
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evaluation of the potential of a substance to affect reproduction;
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evaluation of the potential of a substance to damage DNA; and
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establishment of no observable effect levels.
- See http://www.cdc.gov/nchs/nhanes.htm.