Regulatory Guidelines for Mercury

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Regulatory Guidelines for Mercury at the Workplace

All regulatory agencies that monitor occupational safety levels for mercury universally agree that mercury vapor is highly toxic. Because the use of mercury in various industrial processes creates a risk of mercury exposure to employees, a number of agencies have set guidelines and regulations to monitor and protect workers. These attempts to set a safe level for mercury are an official acknowledgement that, regardless of the source, mercury vapor is a health hazard even at extremely low levels. But understand, these agencies aren’t saying that mercury is “safe”, only that a majority of the people won’t show signs of mercury poisoning while at the workplace and at the arbitrary daily levels they’ve established. As you will see, they don’t all agree on what the so-called “safe” level should be.

Incomplete Regulatory Standards for Mercury

The guidelines set by most of the listed agencies only monitor occupational mercury exposure at the workplace and are based on a 40 hour work week. While these guidelines are great for monitoring mercury during the work day, over 150 million people with amalgam fillings in the United States are being exposed to mercury 24 hours per day, 365 days per year. No regulatory agency has factored amalgams into the equation when monitoring employees’ exposure to mercury. Nor have the guidelines been adjusted to take into account employees’ exposure to mercury from contaminated fish, and environmental sources outside of the workplace.


The National Institute for Occupational Safety and Health (NIOSH) established an exposure limit for mercury vapor of 50 mcg per cubic meter of air (mcg/m3) as a time-weighted average (TWA) for up to a 10-hour workday and a 40-hour workweek. If the monitored air exceeds that level of mercury, employees must leave the area of exposure. (TWA is the average of the sum of all samples taken during a set period of testing.)

The institute struggled with setting the limit because it found a significant portion of the population—those who had never been previously exposed to mercury at the jobsite—already showed early signs of chronic mercury poisoning. That might have confused the people at NIOSH, but when you think how many people with amalgam fillings take in mercury continuously, it’s not surprising that so many already had symptoms related to chronic mercury poisoning.


The Occupational Safety and Health Administration (OSHA) guidelines for elemental mercury vapor are the same as NIOSH, including the same ceiling limit when employees are required to leave the workplace.


The World Health Organization (WHO) settled on an average of 25 mcg/m3 per 8-hour shift for occupational exposure to mercury vapor. The lower guidelines set by WHO are much more realistic because it took into consideration the segment of the population that is extremely vulnerable to mercury and those whose health is already compromised. These population segments include pregnant and nursing mothers, those with compromised immune systems, young children and seniors.


The Agency for Toxic Substances and Disease Registry (ATSDR) takes an approach that is similar to WHO. After a long study, it found that if employees were exposed to mercury in amounts greater than 26 mcg/m3, a substantial percentage showed symptoms related to chronic mercury exposure. Because of this fact, the ATSDR set a minimal risk level (MRL) for chronic exposure to mercury vapor at 3 mcg/m3 per hour over a 24-hour period.

The ATSDR concluded that 3 mcg/m3 per hour is the amount of mercury vapor a person can be continuously exposed to without showing any observable side effects (it doesn’t indicate how long it means by “continuously”, such as continuously over a year, over 10 years?). While not ideal, the ATSDR approach is closer to reality because it acknowledges that people can also be exposed to mercury away from the workplace and from other sources throughout the day and night. Guess who this would include? You guessed right—primarily those with mercury fillings and those eating mercury contaminated fish.

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