Monday, August 30, 2010

CDC Releases New Study on Chemical Exposure

Recently, the Centers for Disease Control and Prevention (CDC) updated information on the levels of 51 chemicals reported in the Fourth Report on Human Exposure to Environmental Chemicals, which was originally released in December of last year. This study examined human exposure to many common chemicals which present potential health risks.

Potentially hazardous chemicals that were found in a large majority of subjects included Polybrominated Diphenyl Ethers, found in many manufactured products, Bisphenol A, often found in plastic food containers such as PC and PVC based water bottles, and Perfluorooctanoic Acid, which is found in the polymer used to produce heat-resistant, non-stick coatings in cookware. On the bright side, the study also found that levels of Lead in children’s blood were declining, as is exposure to environmental tobacco smoke. Levels of the toxic elements Arsenic, Mercury, Cadmium, as well as volatile organic compounds were also explored in the report.

The CDC points out that the report provides “unique exposure information to scientists, physicians, and health officials to help prevent effects that may result from exposure to environmental chemicals.” They plan to use the study to learn more about which chemicals get into Americans’ bodies and at what concentrations, establish reference values in order to determine if an individual or group has an unusually high exposure, and track exposure levels over time.

Little information is currently available about the effects of exposure to environmental concentrations of many of chemicals in everyday use. Studies like this one are essential for providing the information necessary to make good policy decisions.

A summary of the report is available at:

Wednesday, August 18, 2010

Where did the OSHA PEL for H2O2 Come From?

As most of you know, OSHA establishes Permissible Exposure Limits (PELs) in order to protect workers who have the possibility of being exposed to harmful chemicals. PELs are usually expressed as ceiling limits or time-weighted averages for the short-term and long-term – 15 minutes and 8 hours respectively. While knowing these limits are important for anyone that could potentially come in contact with the chemicals, it is also both interesting and helpful to understand where the numbers themselves came from.

In 1954, three scientists performed a series of experiments at the Army Chemical Center in Maryland intended to shed more light on the toxicity of hydrogen peroxide (H2O2) vapor. The study, “Inhalation Toxicity of Ninety Per Cent Hydrogen Peroxide Vapor: Acute, Sub acute, and Chronic Exposures of Laboratory Animals”, involved exposing animals to various levels of H2O2 and observing the health effects. The paper they produced is considered classic research on H2O2 exposure and was the basis for the American Conference of Government and Industrial Hygienists’ (ACGIH’s) threshold limit value (TLV) of 1 ppm for H2O2. OSHA was created in 1970 and it adopted the ACGIH TLV’s as the OSHA PELs a couple of years later.

In the first experiment, rats were exposed to a very high (2880 ppm) concentration of H2O2 for 8 hours. While none of the rats died, they all showed severe congestion of lungs and trachea immediately following exposure. Within 3 days, pulmonary edema occurred and within 14 days, the majority of lungs showed many areas of alveolar emphysema as well as severe congestion. What the scientists learned was that while there was initially minor irritation, more severe symptoms developed later. There were similar results when the concentration of H2O2 was reduced to 243 – 308ppm for 8 hours.

In the second experiment, rats and mice were exposed to about 67ppm of H2O2 vapor for 6 hours a day, 5 days a week, for 6 weeks. Results included profuse nasal discharge after 2 weeks of exposure, hair loss around the nose in the 5th week (most likely due to animals scratching to relieve irritation), high rates of death among mice (80% after 18 exposures), and some congestion in the lungs.

The third experiment, however, was perhaps the most telling. In this series, dogs were exposed to 7ppm of H2O2 for six hours a day, five days a week, for 6 months. It was found that while there were no toxicity signs for the first 23 weeks, long-term exposure caused baldness, hair bleaching, and permanent lung damage, as well as general irritation such as sneezing and lacrimation.

Because of these results, the scientists concluded that long term exposure to even low concentrations of ~7ppm or more will produce impermanent lung damage in animals. Furthermore, one of the most important results from the study is that health effects resulting from exposure often do not appear immediately, and often present themselves days, or weeks later. From an occupational health perspective it should be noted that hydrogen peroxide has almost no odor and so is imperceptible until well above the OSHA PEL of 1 ppm. Therefore, continuous monitoring of the workplace to prevent exposures before they occur is recommended for all facilities using high concentrations of H2O2 where there is the potential for employee exposure.

Thursday, August 12, 2010

Should OSHA’s Standard for Ethylene Oxide be Revised?

We touched on this topic a couple of weeks ago when discussing generally if OSHA should consider updating its regulations of chemical sterilants. We came to the conclusion that it should, as there has been a large amount of new data on many chemicals commonly used in sterilization and disinfection, but that enforcement would be a key issue as well. This week, we’ll take a closer look at OSHA’s standard for Ethylene Oxide (1910.1047), which exists to protect those who may potentially be exposed to the sterilant gas. Specifically, we will focus on section d of that standard – “Exposure Monitoring”.

While the ultimate goal of the standard is to promote worker safety, section d serves to create a false sense of security for those using EtO at their facility. This section requires employers to take initial measurements and then, if the standards are met at that time, states that it is not necessary to measure again for as long as 6 months in some cases. Going against all logic, this section seems to claim that if there is not a problem now, there will not be one in the future. As we all know too well, equipment can fail, and accidents can and do occur.

What is the solution to this problem? Enforcing a simple Permissible Exposure Limit (PEL) would require employers to ensure that there is a safe work environment. Continuous monitoring of the workplace would ensure that employees are safe at ALL times, instead of just the times samples are taken as currently required in the standard. The bottom line is that accidents are always somewhat unexpected events. Telling employers that they “may rely on such earlier monitoring results to satisfy the requirements” greatly increases the likelihood that accidental leaks will not be detected.

When 1910.1047 was drafted in the early 1980s, continuous monitors were not readily available, which is certainly not the case today. Revising the EtO standard to match current technology is something that must happen if the goal of the document is to promote worker safety above all else.

1910.1047 can be found here:

Monday, August 2, 2010

Why do people think Hydrogen Peroxide is less hazardous than Ethylene Oxide?

When you look at the EtO standard, 1910.1047, the first thing that comes to mind is that it is an enormous amount of information. The standard is very long and detailed concerning the use, storage, and monitoring of EtO. When you then research the H2O2 standard, it appears to be a simple one liner in 1910.1000. It would follow from this observation that H202 is much less hazardous than EtO because OSHA did not dedicate an entire standard to it as they did with EtO.

However, what you may not realize is that H2O2 is covered by more than just 1910.1000. It is also covered by the hazard communication standard (1910.1200), the emergency action plan standard (1910.38) and other standards. If you combine all these other standards, then the EtO standard does not look so much larger. It is important to remember that in the 1980s, EtO became recognized as a probable and later as a known human carcinogen, so OSHA developed individual standards for several known human carcinogens including EtO. H2O2 is generally not considered to be carcinogenic, although ACGIH says it is an animal carcinogen, and so hydrogen peroxide is covered under 1910.1000, where EtO used to be.

For comparison, OSHA’s 8 hour Permissible Exposure Limit (PEL) for both EtO AND H2O2 is 1ppm. However, NIOSH’s Immediately Dangerous to Life and Health Level is only 75ppm for H2O2, but 800ppm for EtO. While H2O2 is not a known human carcinogen, it can still inflict serious harm on those who are exposed such as permanent lung damage and neurological deficits.

To peruse the relevant standards, follow these links: