Volume 18, Number 1 .... January 1996
For some time this column has focused on estrogen mimics or xenoestrogens. It is a new year and time to wrap up this important topic and look for other ways to frighten readers of the WAAC Newsletter.
There have been some very interesting developments with regard to chemicals that mimic estrogens in the human body. [These chemicals appear to act as hormones and may be linked to many of the ills of 20th century man (50% decrease in sperm count and tripled rates of testicular cancer over the last 50 years) and woman (the explosive increase in breast cancer and endometriosis). Readers unfamiliar with the topic might want to refer back to this column in last year's January issue (V. 17, n. 1) of the Newsletter as well as the May '94, and Sept. '91 columns. Of special interest to conservators: Triton X-100, Aroclor, and Bisphenol A, a component of epoxy resin are xenoestrogens. If these chemicals do adversely affect the human body, they do so at very low levels of exposure.]
I hadn't seen references to Bisphenol A's status as an estrogenic mimic until recently. It is used as one of the starting reactants in the resin component of most epoxies. It is also used in the production of polycarbonate plastic and can be released when that plastic is heated. The indirect evidence against Bisphenol A is pretty strong - some male plastics' workers developed breasts after chronically inhaling dust containing the chemical.
The October 1995 issue of Scientific American contains the article "Can Environmental Estrogens Cause Breast Cancer?" (pages 166-172) by Devra Lee Davis and H. Leon Bradlow. This important article leaves many questions unanswered, but its appearance in a magazine with Scientific American's credentials gives considerable weight to the authors' thesis. I'll discuss this more after mentioning some other material that has been published recently.
Appearing in the same issue of Scientific American, in "Science and the Citizen", is a sobering item, "Deaths Caused by Breast Cancer, By County", page 32D. In a scene right out of one of my favorite obscure movies, "Bliss" (1986, Australian, directed by Ray Lawrence), we are presented with a cancer map. The map of the United States is color coded by county to show the average number of deaths per 100,000 age-adjusted white women ages 35-84. The areas show a complicated pattern based on deaths of: less than 45 per 100,000; 45-54.9 deaths; to over 55 deaths per 100,000.
The cancer map confirms some known risk groups, e.g., that Mormons have very low rates of breast cancer, that women who don't have children or have them when they are older than 35 are more at risk. Alcohol consumption also correlates with the map. However dietary fat intake as a predictor doesn't correlate with the geographic based data. Quoting the author, Rodger Doyle: "The controversial notion that environmental chemicals cause or promote cancer is also supported: the distribution of toxic-waste dump sites parallels fairly closely the sites of highest breast cancer mortality."
Leslie Bone sent some clippings from The Times (London) with titles like:"Tinned vegetables may pose threat to male fertility" (8/95), "Hormone-change chemical added to list of hazards" (6/95), and "Why our men are getting less fertile" (8/95).
The article on tinned vegetables reports on research that has found that Bisphenol-A from epoxy resins used in can coatings has leached into the contents of canned foods. The liquid removed from canned vegetables was tested on cultured human cells. 60% of the samples showed estrogenic effects that correlated with the Bisphenol-A levels in the liquid. The June article notes that Britain has proposed that nonylphenol be added to the list of hazardous chemicals to be banned by the European Commission.
The article on male fertility discusses the research of Dr. Richard Sharpe. His work suggests that the 50% decline in sperm count over the last 50 years results from "damage to the male foetus during the first three months of development in his mother's womb... The most likely cause of this damage is environmental chemicals...which mimic the effects of the female hormone oestradiol [British spelling of estradiol, the most potent naturally occurring estrogen]." Dr. Sharpe's personal recommendation, actually what he practices with his own family, is to avoid anything containing soy products.
Let's consider all the above along with the Scientific American article "Can Environmental....". The authors discuss known causes of breast cancer. The putative defective gene only accounts for about 5% of cases. Combining all known risk factors, only about 1/3 of the number of cases can be explained statistically. The authors present evidence that estrogenic chemicals might be in part responsible for the other 67%.
They discuss that there are two types of xenoestrogens: those that reduce the effects of estrogen produced in the body; and those that amplify or mimic the hormone's effects. The compounds that interfere with estrogen receptor sites include soy products (remember Dr. Sharpe's advice), broccoli, cauliflower and tend to be degraded quickly in the human body. Those that trigger estrogen's receptor sites include the chemicals mentioned in previous H&S columns, modern synthetic chemicals like DDT, some PCB's, nonyl- and octylphenols (Triton X-100), and Bisphenol-A.
The authors also have an interesting explanation for the purported relationship between breast cancer and estrogen mimics. They note that estrogen is metabolized in the body by two different mechanisms. One produces 16-alpha-hydroxyesterone and the other 2-hydroxy-esterone. The 16- metabolite is the so-called "bad" and the 2- "good" (sort-of analogous to the good/bad cholesterol thing).
It appears that at least some of the xenoestrogens shift the metabolism mechanism from that which yields the 2-hydroxy- to the 16-alpha-hydroxy- product. DDT and its breakdown product DDE increase the 16-alpha- metabolite in cultured breast cancer cells. Other research shows that the presence of the natural plant xenoestrogens (broccoli, brussels sprouts, cabbage, and cauliflower) tends to favor the production of the "good" metabolite. The authors note that soy products appear to do the same.
But what does it all mean? I'm not sure, but I have some suspicions. Is it another example of science gone bad, with researchers finding correlations that sound great but are later proved to be wishful thinking combined with sloppy work? I doubt it. Will xenoestrogens be found to be the sole cause of 2/3 of he cases of breast cancer? Again, I doubt it. Would I stop using Triton X-100? I already have. Will I be much more cautious with epoxies? You bet. And what about Dr. Sharpe's 'no soy products' recommendation? Based on what I've read, I would say he is wrong. In fact, I think it looks as if the soy products and broccoli and related vegetables are something of an antidote to the bad xenoestrogens.
A New Year's column? The above represents the out with the old. Now for in with the new (bad news).
Readers have wondered about their exposure to lead while working on paintings. This is a very interesting question. Their informal testing of work surfaces after having removed a lead primed lining canvas and an old lead white fill showed contamination. But there are more general questions, too. What about leaching of lead from an oxidized, unvarnished paint film? Is lead (or are other heavy metals) available to be absorbed through the skin? What about spit cleaning? How mobile is the lead, can it be washed into cleaning swabs?
And it is not just paintings conservators who may be exposed. Do cotton gloves provide any protection when handling metallic lead objects? What if you wash those gloves with other laundry? What is the best way to clean up after generating lead bearing contamination? If you think you have been exposed, within what time frame will blood level lead testing give an accurate indication of that exposure?
This is a call for anyone who is worried about lead exposure at work or anyone who has been part of a testing program or looked into these questions to please contact me.
Preliminary research has turned-up some interesting facts. Home lead test kits can be used to confirm work-space lead contamination. All studios should probably budget for an HEPA vacuum system to avoid blowing lead (and other toxic contaminants) into the air while cleaning-up. There are established procedures to clean a work surface after working on a project that may have generated lead contaminated dust. The most interesting aspect was the use of trisodium phosphate (TSP) as the cleaning agent. (The phosphate complexes soluble lead, rendering it non-bioavailable.)
Please keep those cards, letters, and e-mails coming.Chris Stavroudis is a conservator in private practice.