Sulfuric Acid Mist
Judged Cancer Agent
UE News, December 1998
R
ecently the International Agency for
Research into Cancer (IARC), a respected international science group based in Europe,
classified sulfuric acid mists as causing cancer in humans. Specifically, the IARC
concluded, "There is sufficient evidence that occupational exposure to strong
inorganic acid mists containing sulfuric acid is carcinogenic." Also, the American
Conference of Government Industrial Hygienists (ACGIH) has for several years listed
sulfuric acid mists as a "suspected human carcinogen."
These conclusions are based on worker health studies in a number of
industries involving exposure to sulfuric acid mists. Thus workers in fertilizer plants,
steel pickling plants and chemical and soap manufacturing have shown increases in lung,
nasal and larynx cancers. An acid mist is a suspension of acid droplets in air. (Skin or
eye contact with sulfuric acid, while dangerous in their own right, do not appear
to cause increased rates of cancer.)
COMMONLY USED CHEMICAL
This new classification of sulfuric acid mist as cancer causing is of
special concern because sulfuric acid is one of the most commonly used industrial
chemicals. In the U.S. alone, more than 40 million tons of sulfuric acid are
manufactured and used each year. The National Institute for Occupational Safety and Health
(NIOSH) estimates that more than 200,000 U.S. workers are regularly exposed to sulfuric
acid.
Sulfuric acid baths are used in electroplating, as well as metal cleaning,
etching and pickling processes. Sulfuric acid is widely used in car and truck storage
batteries, and thus workers who manufacture, recycle or recharge batteries may be exposed
to hazardous acid mists. Also, sulfuric acid is used in the production of phosphate
fertilizers, in pulp mills and paper manufacturing and in the production of textile
fibers.
The OSHA legal limit for sulfuric acid exposure is 1 milligram of sulfuric
acid per cubic meter of air (1 mg/m3). Also, ACGIH
further recommends a 3 mg/m3 short-term exposure limit
during any 15-minute work period.
The main health effects of short-term exposure to sulfuric acid vapors and
mists are irritation and burning of the skin and the moist tissues of the eyes, nose and
throat. Breathing in acid vapors and mists can cause chest tightness and shortness of
breath. If the exposure continues, the burning and irritation of the lining of the lungs
can cause fluids to collect in the lungs, which can lead to pneumonia, respiratory failure
and death. Until recently, it was not recognized that heavy exposure to sulfuric acid
mists could also lead to respiratory system cancers. The finding is of special concern to
workers who smoke cigarettes, since they are already at elevated risk of lung cancer.
It should also be noted that the OSHA sulfuric acid standard was adopted
long before this acid was suspected as a cancer agent. Since there are currently no known
safe levels of exposure to cancer agents, union health and safety committees should work
to prevent all unnecessary sulfuric acid mist exposure. We should be guided by the ALARA
Principle, used to protect nuclear industry workers: Seek exposure levels As Low
As Reasonably Achievable.
PROPER VENTILATION NEEDED
The most important single factor in reducing sulfuric acid mist is to make
sure that all acid tanks and acid processes are properly ventilated. For open
tanks, as in electroplating, so-called push-pull ventilation is recommended, which pulls
mists away from workers’ breathing zones. Also, many battery recharging areas within
plants are poorly ventilated. In this process, when explosive hydrogen gas is released, it
bubbles up in the acid bath and lots of sulfuric acid mist may be generated. Based on our
new cancer information, these battery-charging areas need to be very well ventilated,
which will prevent both hydrogen gas and sulfuric acid mist buildup.
In general, if you or others are experiencing eye and throat irritation
near sulfuric acid processes, consider this an early warning sign of possible sulfuric
acid overexposure. In this case ask management through your union officers or health and
safety committee to measure the level of sulfuric acid in the workroom air. And remember,
if the level is below the OSHA limit of 1 mg/m3, this may
get OSHA off your employer’s back (for the moment), but this is no longer adequate
protection for you or your union sisters and brothers. Remind your employer that sulfuric
acid mist is now considered a human cancer agent, and that it is necessary to reduce the
level of exposure to be as low as reasonably possible. And no, respirators are not the
answer to this problem — they leak, they are uncomfortable and they don’t
protect people who work nearby or pass through the hazard area on occasion. Proper,
well-maintained exhaust ventilation is what is needed to reduce hazards for all in the
shop.
Also, it is important to check the sulfuric acid Material Safety Data
Sheets (MSDSs) in your plant to make sure that they are up-to-date and reflect this cancer
information. If they don’t, this needs to be brought to the attention of management,
and they need to request new, updated MSDSs from their suppliers. Furthermore, any hazard
communication training in the future needs to reflect this new understanding of sulfuric
acid hazards.
And finally, since this is December, have a safe and happy holiday
season!
