PROBLEMA DE CARÁCTER GLOBAL

one must always be aware of the potential risks and then take actions designed to re- duce the risk to an acceptable level. This is a personal choice, based on one's own risk- tolerance and the perceived and actual costs of the risk management. To give an example, consider speeding tickets - some people feel it is too costly (time, boredom factor) to drive slowly and are willing to accept a higher risk of getting a ticket, while other people are ei- ther willing to invest the extra time or to in- vest the money to purchase a radar detector. The purpose of this month's column is to help the reader understand a little more about the risk factors in handling certain pyro chemicals, and to help them find their own information. Then the reader can make their own decisions about their risk toler- ance, and how much they are willing to in- vest to manage those risks.

First of all, there are several good sources of information about the risks associated with chemicals; the MSDS which should be in- cluded with every chemical you purchase, "The Merck Index", Sax' reference entitled "Dangerous Properties of Industrial Materi- als", and the Internet. The MSDS sheets are generally good sources of information, but they must be read with the understanding that behind every MSDS there is a lawyer playing "CYA". How else can one explain that the MSDS for Lactose (also known as milk sugar) states that ingestion requires imme- diate medical attention and that skin contact should be followed by 15 minutes of washing with soap and water? However, the lawyers haven't completely ruined the MSDS sheets. The MSDS rates each chemical for various hazards on a scale of 0 (no hazard) to 4 (severe hazard), and then gives some specific details about the types of hazards. Thus we can find that lactose is not carcinogenic, is not listed by OSHA, h a s no known effects for overexposure, has no target organs, etc. This seems like a pretty benign chemical!

Compare that with ammonium or potassium dichromate: It is listed as a carcinogen with very low permissible exposure limits (0.5 mg/cubic-meter in air). The MSDS goes on to

state that skin contact may cause ulcers, discoloration and eczema, and prolonged ex- posure to dust may cause perforated septum and ulcerate the mucous membranes. Inges- tion may cause nausea, vomiting, headaches and dizziness along with gastrointestinal irri- tation. It concludes that skin absorption may be harmful or fatal. Pretty awful stuff, eh? Well, seeing this got me worried - as a kid I used to play with a lot of ammonium dichro- mate, making volcanoes and growing crys- tals. Many times I went to bed with orange or brown fingers. I was worried if this meant that I was going to get cancer. So, I did a bit of research. First place I looked was in "The Merck Index". This is an EXCELLENT refer- ence book and is a steal at only $45. The en- tries of the Merck Index did mention the acute effects, but failed to mention the car- cinogenicity. Moreover, it listed a host of common uses for each chemical ranging from tanning leather to printing to bleaching palm oil. My first thought on reading that was, it might not be so horrendously dangerous - after all, with such widespread usage it can't cause cancer "first time every time" or they would have stopped using it.

So my next place to look was in Sax' refer- ence work "The Dangerous Properties of In- dustrial Materials". Once again I received conflicting signals. The individual entries for ammonium and potassium bichromate (an older term for dichromate) stressed the acute toxicity, but didn't mention anything about cancer. The general entry for "chromium compounds" stated that they are "recognized carcinogens of the lungs, nasal cavity and paranasal sinus". This entry was much less strenuous than those for compounds that I have worked with in the lab which are con- sidered "dangerous but useable without he- roic protective measures".

Thus, I turned to the Internet to see if I could find more details. I performed several searches using search engines such as www.excite.com and www.alta- vista.digital.com, using combinations of key- words including "chromium", "dichromate", "cancer", "carcinoma", "epidemeology", etc.

When one uses the web one h a s to learn how to be a good critic since anyone can "publish" anything on the web. I found literally h u n - dreds of documents ranging from the scien- tifically rigorous to the eccentrically amusing (cancer therapy by the use of chromium plated electrodes to directly introduce 'elec- tro-orgone energy' into the body to reharmon- ize the natural blah-blah-blah). The docu- ments which survived a culling based on rigor/fluff were not all in total agreement, but I began to see a pattern when all of them were looked at as a whole.

The most dramatic document was one from the Health Resource Group (associated with Ralph Nadar). They are filing a suit in court demanding that we put increased restriction on chromium. This brief estimates that the current Permissible Exposure Level will lead to 22% of the people so exposed dying of lung cancer! YOICKS, 22%! However, all subse- quent reports seemed to be much less dra- matic. OSHA estimates that an exposure to a chromium level which is 6 times higher will lead to about 8 deaths per 1000 people. Early epidemiological studies on people who worked in chromium smelting plants in the 40's and 50's found that such people were 13 to 31 times more likely to get lung cancer than the general population. Of course there was a large synergism with smoking. Many cancers seem to operate by the so-called "two assault" mechanism, where one assault cre- ates the opportunity for tumor growth, and the second different assault then initiates the tumor.

In 1975 NIOSH found a correlation between solubility and cancer. The soluble salts are apparently less carcinogenic than the in- soluble ones. Thus, dichromate might not be so bad, but the dust from the coating of Mg might be worse. This is supported by a study that found that chromate pigment plant workers with an exposure to 218 - 413 (µg/m3 had an "elevated risk". A study on 1,879 workers found that people who had worked in the plants for more than 10 years had three times greater incidence of lung cancer than the general population. However, the same study found that people in more mod- ern plants with levels from 12 to 120 (µg/m3 showed no statistically significant increase.

A study on 1,193 workers in a chromium plating plant who worked for more than 16 years found a 1.18 times increase in lung cancer and a 2.34 times increase in liver cancer. A study of 5,000 people who worked in chromium and chromate plants from 1937 to 1971 found a 1.51 times increase in lung cancer overall, and a 1.94 times increase in those people who had worked in those plants for more than 20 years. They did find a much higher incidence (5.18 times increase) in na- sal cancer.

Several studies found a fairly linear effect of total chromium load and cancer for airborne levels from 10 to 500 (µg/M3. Thus, it may be assumed that a higher level in the air may very well be proportional. Little or no acute toxicity was found for short term exposures to very high levels of chromium, chromate, or soluble chromium salt dusts. However, it probably h a s some increased cancer risk. Of course, nothing is ever simple. A study of 62,641 women found that post menopausal women had a slight increase in breast cancer with increased levels of chromium exposure, but that premenopausal women had a DE- CREASE. They concluded there was no sig- nificant risk at the levels examined.

The final conclusion that I reached was that long term exposure to chromium dusts and chromium salts would increase my cancer- risk, but that the risk was acceptably low. Thus, while I will continue to use a respirator and gloves when handling chromium com- pounds, I am not worried that an accidental short exposure is a serious risk. However, that is a personal choice based on my risk tolerance, and as the ads say "your mileage may vary".

The important thing about this article is not just an assessment of the risks of chromium in the pyrolab. The real point is that it is im- portant that every pyro know how to discover the pertinent information themselves so that they may make their own informed decisions. The Merck Index should be on every pyro's shelf, and everyone should start learning how to use the Internet. While there is a lot of poor information out there, it is possible to winnow through the chaff to discover the hard facts. TIP

PYRO ROULETTE - SAFETY ISSUES