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The percentage of preterm births in the United States has risen 36% since 1984.
US Department of Health and Human Sciences Centers for Disease Control and Prevention

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Pregnancy & Work
Case Studies

Exercise 1 - Carbon Monoxide

Background: Heightened concern: In 1997 the California Supreme Court ruled that a child could sue her mother's employer (and supervisor) for birth defects allegedly caused in-utero from her mother's exposure to carbon monoxide while at work. The case was settled for an undisclosed sum before it was heard at the trial court. The case was addressed in the February 26, 2002, USA TODAY cover story "Workers take employers to court over birth defects: Workplace hazards worry employees, their children."

Scenario: A manufacturing plant employs 275 employees, with 42% being female. Employee age ranges from 19-63 years with an average age at 27. The plant has lost sales from foreign competition and capital budgets are frozen except for critical needs.

Carbon monoxide (CO) has been measured in the manufacturing and shipping areas and occasionally reaches 15 parts per million (ppm) as an 8-hour time weighted average (TWA). Sources of CO are from heat-treating ovens and forklifts. Ceiling concentrations at 38 ppm and 48 ppm (30 minute exposure) have been measured, respectively, for employees working at the shipping area and near the heat-treat oven. CO exposure has not been measured for maintenance employees that occasionally conduct repair welding work. The CO results have been consistent for at least five years.

The plant safety and health (S&H) manager conducts new hire and annual OSHA hazard communication training. The plant S&H manager has informed employees about the hazards & risks of carbon monoxide during the previous five years by explaining:

"Carbon monoxide is a colorless and odorless gas that can be formed by the incomplete combustion of products that burn. CO competes with oxygen in the blood. It's a fairly common story that in the wintertime poorly vented stoves in homes may produce CO and overcome some people. Over-exposure to CO may cause headaches and drowsiness, and in extreme cases death. Pregnant women are at increased risk from CO exposure. CO measurements in our workplace are below OSHA limits."

An employee with five years seniority informs the S&H manager that she intends to have another child and she is concerned about her exposure to CO. Her first child, now three years old, was born with spina bifida. The employee states she recently found online a research study from the National Institute of Environmental Health Sciences entitled: "Molecular Basis of Carbon Monoxide Induced Spinal Abnormalities." The summary of the study includes: "The results strongly indicate a functional link between CO exposure during early embryonic development, Paraxis gene expression, programmed cell death, somatic abnormalities, and vertebral defects."

The plant does not have a workplace reproductive & developmental health program. The corporate position on the issue is that these programs are discriminatory and that "decisions about the welfare of future children must be left to the parents who conceive, bear, support and raise them rather than to employers who hire those parents." The plant manager believes that compliance with OSHA regulations is all that is legally and morally necessary to protect employees from workplace hazards.

The safety and health manager conducts a literature search on CO and finds the following with regards to exposure.

SourceExposure Limit(s)Notes
Published Toxicological Study90 ppm 8-hoursLOAEL – adverse fetal and neonatal weight gain
Occupational Safety & Health
Administration (U.S.) – PEL

50 ppm 8-hour TWA

Does not address repro/develop health
National Institute for Occupational Safety & Health (U.S.) – REL

35 ppm 10-hour TWA
200 ppm ceiling

Does not address repro/develop health

German Ministry of Labor
MAK exposure limit

30 ppm (work-shift) TWA

International Chemical Safety Card (2004): "Harmful effects probable during pregnancy in spite of observance of MAK"

American Conference of Governmental Industrial Hygienists

25 ppm 8-hour TWATLV® basis includes "Reproductive" as a critical effect
Ministry of Social Affairs and
Health (Finland)
14 ppm 8-hour TWASuggested limit for pregnant employees
Jankovic and Drake 112 ppm 8-hour TWACalculated Occupational Reproductive Guide
10 ppm 8-hour TWA
1 Jankovic, J. and Drake, F.: A Screening Method for Occupational Reproductive Health Risk. Am. Ind. Hyg. J. 57:641-649 (1996).

2 World Health Organization, Air Quality Guidelines, Second Edition, 2000.

Exercise 2 - Breast-Milk

The December 2002 issue of Pediatrics reports that breastfeeding among fulltime employed U.S. women is now at 25%, nearly double its rate from 1996, and the highest rate ever recorded. Employers may expect continued growth in breastfeeding among working women due to changes in public health policies, new state laws, and better support for this practice. Mothers may pump and store their breast-milk at work and provide this food to their infants at another time.

Breast-milk is superior over baby formula because it includes the mother's disease fighting antibodies along with great nutrition. And there's benefit for the mother, too. New research finds that women who breastfeed have a 50% less chance of developing breast cancer, although more studies are needed to determine why this is so. The American Academy of Pediatrics stresses that breastfeeding is no longer considered a lifestyle choice, but an important health choice for both the mother and infant.

Along with the rise in breastfeeding is a rising concern over chemicals in breast-milk. The US Food and Drug Administration advise on which pharmaceuticals should not be used while breastfeeding, aspirin is an example. There is limited study and guidance regarding environmental e.g. workplace chemicals in breast-milk.

Biomonitoring e.g. measuring chemicals in human tissues and fluids is a rapidly evolving technology. Breast-milk is a popular body fluid to monitor because it is the least invasive and best means to sample for chemicals stored in body fat. In 2004, the California senate passed legislation requiring the monitoring of chemicals in breast-milk to determine a possible linkage between chemical exposures and health effects. Germany and Sweden already have such a law.

In September 2003, two US studies of breast-milk found levels of polybrominated diphenyl ethers (PBDEs) used as flame-retardants in products such as electronics, at 10 to 20 times higher than those in Europe. The EU banned PBDEs in 2004 due to concerns that these chemicals may cause developmental problems in breastfed children.

Media reports on chemicals in breast-milk are growing. In January 2004 the Wall Street Journal published the article "Toxins in Breast-Milk: Studies Explore Impact of Chemicals on Our Bodies." And promptly thereafter, the American Chemistry Council posted online an Issue Brief on "Human Milk and Biomonitoring."

A Google search for yielded 21,000 sites in December 2002. March 2004 over 63,000 sites; February 2005 over 174,000; and, March 2008 there were over 1 million sites. Studies by the American Medical Association show the majority of Americans use the Internet to help them answer health questions.

Some harsh approaches are being taken when toxic chemicals are found in breast-milk. A woman in California, for example, was sentenced to life in prison in 2003 when methamphetamines in her breast-milk were found to be the cause of death for her three-month-old son. And other states have charged people for murder, too, for similar "toxic breast-milk" offenses.

1.Do employees that breastfeed have a right to know if workplace chemicals may be in their breast-milk?
2.Will breast-milk be safe for infant consumption if an employer is in full compliance with OSHA chemical exposure standards?
3. Does an employer have a legal obligation to protect an employee's breast-milk from contamination caused by exposure to workplace chemicals?


Does an employer have a moral obligation to protect an employee's breast-milk from contamination caused by exposure to workplace chemicals?


Does OSHA prohibit the storage of breast-milk in a refrigerator, if the refrigerator is also used for storage of food for employee consumption?
6.Is an infant biologically equivalent to a small adult?
7.Has the U.S. Food and Drug Administration established safe limits of industrial/environmental chemicals in breast-milk?
8.Can the concentration of chemicals in breast-milk ever be higher than found in the mother's blood plasma?
9.Do you believe research, within the next two years, will discover infant health problems that result from breast-milk contaminated by a common industrial chemical?
10.Has the ACGIH recommended any Biological Exposure Indices for workplace chemicals in breast-milk?
11.Should an employer abide by all recommendations from an employee's pediatrician with regards to safeguarding breast-milk from contamination at work?
12.Is a recommendation, by a pediatrician, for an employee to avoid all workplace contact with lipid soluble chemicals practical?


Do supplier material safety data sheets (MSDS) provide sufficient information to determine if a chemical may concentrate in breast-milk?

90 ppm 15 minutes
U.S. Environmental Protection Agency

35 ppm 1 hourOutside air considering all ages
9 ppm 8-hour TWA

14.Are infant health problems alleged to result from breast-milk contaminated with workplace chemicals handled through the employer's workers' compensation program?
15.Is it in an employer's best interest to address health concerns arising from information that the employee finds online?
16. The EU requires, when applicable, the following "risk" phrase on safety data sheets: R64 May cause harm to breastfed babies. Does EU safety data sheets impact MSDS for US employers?


If an employee is not satisfied with an employer's position on protecting breast-milk, is the employee's only option to quit work?


Are murder charges for toxic chemicals in breast-milk a reasonable legal action?

  1. What should the S&H manager do/not do to address the employee's concerns?
  2. What limit above, if any, is "safe"? Explain "uncertainty."
  3. What should the S&H manager do/not do to protect the company?
  4. Is the corporation's belief on reproductive & developmental programs correct?
  5. What should the S&H manager do to protect himself/herself from potential liability? If you feel no liability exists, explain why.
  6. A CO exposure at 50 ppm 8-hr. TWA produces COHb at 8-10%, as will smoking 20 cigarettes per day. What, if anything, should the S&H manager do with this information?
  7. What additional questions should be asked to better address this exercise?
  8. Are there any ethical or moral dilemmas to consider e.g. when did the IH's responsibility for fetal protection begin?
Maternity Protection - Helping employers help families.