September 1997 Volume 19 Number 3
The last episode, ended in a cliff-hanger. You've all probably spent the summer wondering about lead poisoning and, "Did Chris buy a HEPA vacuum?"
To forestall your skipping to the end of the column for an answer, you will be thrilled, no doubt, to learn I did purchase a HEPA filtered vacuum. More about that later.
But, perhaps we should review.
My point in the previous column was that many conservators are probably exposed on occasion to lead in our work.
Lead is very bad (see the prior issue of the Newsletter). It is a heavy metal toxin that accumulates in the body.
Paintings and frame conservators: When you brush out a frame's rabbet, do you wonder about the fine dust that is generated by the slow rubbing between the painting and the frame? Might the ground or paint layer that it came from be lead based? What about those small flakes of friable ground that often shed from the tacking margin?
Objects conservators: What about lead objects? Bronzes made with high lead levels? When there is corrosion present, do you wonder if it is lead carbonate or lead formate? Ever scraped old solder joins from metal?
Everyone: Do you use lead weights? How well sealed are they? Is that lead shot in those cute little squishy weights? Have you ever had to reverse a mend (or lining, or fill) made with what could have been lead white?
And, as lead is a cumulative poison, other forms of exposure count, too. We are exposed to lead in our non-professional lives as well. A 1991 article in Newsweek1 presented the following grim statistics: "Seventy-four percent of all private housing built before 1980 contains some lead paint"; "Three million tons of old lead line the walls and fixtures of 57 million American homes"; "One of nine children under age 6 has enough lead in his blood to place him at risk"; and "Children with high lead levels are six times more likely to have reading disabilities."
Research has shown that lead can be leached out of a mother's bones and contaminate the tissues of her developing fetus during the second and third trimesters of pregnancy2. [The doctor quoted in the summary said that calcium supplements taken during pregnancy might help by reducing the fetus' demand on the calcium in the mother's bones.]
Many calcium supplements include unhealthy amounts of lead. (Don't you just hate it!) California's Prop. 65 may force all drug companies to change their processing procedures to avoid being forced to add a warning label to their calcium tablets. In the meantime, calcium from Leiner Health Products Corp. has been treated to be virtually lead free (at a wholesale cost of 20% more than tainted calcium) and is used in many brands of supplements. Some of the brand names include Longs' Calcium & Magnesium, Walgreens' Calcium 600 USP, and Your Life's Natural Calcium & Magnesium USP and Natural Calcium, Magnesium & Zinc USP. Tums 500 Calcium Supplement (chewable) and Mylanta Children's Antacids have lead levels below the Prop. 65 limit.3
In a real sense, we are all lead poisoned already. Prior to the industrial revolution, the total body burden of lead was about 2 mg. Now it is about 200 mg. Typically 150-250 �g of lead is ingested per day and 5-10% is absorbed into the body.4
Avoid moonshine whiskey (20%-90% of moonshine samples contain lead in the potentially toxic range).
If you are at risk of exposure to lead, seriously consider starting your own lead level surveillance program. This is particularly important if you are planning to have a child and applies to both female and male conservators. It is also important if you work and live in the same physical space.
When your doctor orders blood tests ask her/him to add a blood lead level to the panel. If you are at special risk, discuss a surveillance plan with your MD. Blood lead levels taken every six months might be a reasonable place to start.
There are two types of lead blood analyses available: whole blood lead level and zinc protoporphyrin (ZPP).
Whole blood lead levels are great at detecting chronic exposure. But lead only stays in the blood for a relatively short time before settling into soft tissues and bone--a period of weeks to no more than a month or two after exposure. With intermittent exposures, timing is everything. That is why it is critically important to have your blood lead level checked immediately after an incident where you suspect you were exposed to lead.
The ZPP test measures the effect lead has had on your blood chemistry. Lead interferes with the binding of iron into the oxygen carrying heme protein found in red blood cells. In the place of iron, the body incorporates zinc producing ZPP.4 The presence of ZPP can be determined in the blood for some months after exposure, long after whole blood lead levels have returned to normal.
Still drinking coffee in the workplace? DON'T! It turns out that coffee increases lead uptake. If there is lead present in your environment this is a great way to render more of it bioavailable. For that matter, eating and drinking in general should not be allowed in a conservation work space.
A reader suggested that we could use steel shot instead of lead shot in our weights. You will probably agree with duck hunters (possibly for the first time) that it is not as good as lead, but it is unquestionably safer.
Over the last few months I've spent a good deal of time thinking about our lead problem. After encapsulating your lead weights and becoming aware of the problem, the best thing you can do to minimize exposure to lead (as well as arsenic, asbestos and other particulate nasties) is to invest in a HEPA vacuum and to use it regularly.
We are professionals. We have no business using conventional vacuum cleaners or brooms in a professional setting. Conventional vacuums (and sweeping, to an even greater extent) take some of the finest particles you are attempting to remove and blow them back into your breathing space. HEPA and ULPA filtered vacuums don't.
What do those funny words mean? HEPA -- High-Efficiency Particulate Air filter is rated to trap 99.97% of particles 0.3 microns and larger. ULPA -- Ultra-Low Penetration Air filter traps even more, 99.99% of particles 0.12 microns and larger. (See the Technical Exchange submission by Batyah Shtrum for more information on HEPA and ULPA vacuums.)
I am now the proud owner of a Nilfisk GS90 -- their allergy vacuum. I was also very impressed with the WAP SQ10. The Nilfisk GS80 is the museum standard for HEPA vacuums and is also a wonderful machine.
The week before I bought my GS90, Nilfisk decided that it would only be sold with the ULPA filter. I was able to purchase the last (albeit slightly used) GS90 equipped with a HEPA filter at my local dealer for $515. There may be more floating around in the distribution chain at more or less that price. You should be able to find the ULPA version for about $725. The GS90 has the identical motor and filtration system as the industrial GS80 ($877). The GS90 has a squarish plastic canister fitted below it's R2D2-like head while the GS80 has a heavy duty stainless steel canister with outboard wheels for better stability.
The GS80 is normally sold with the HEPA filter, but the ULPA is an option. Either filter will fit on the machine. Many Nilfisks used in conservation departments are also fitted with a motor speed control, a $225 option. If you plan to run your expensive vacuum at reduced speeds, you should probably invest in a motor speed controller rather than just using a lamp dimmer switch. You should also know that most vacuums don't like being run at lower than normal speeds.
The WAP SQ10 is even quieter than the Nilfisk and has stronger suction. It is a low profile, kind-of cube looking, shop-vac style machine. The HEPA filter is extra -- make sure you replace the standard PE-fleece filter with a HEPA cartridge. It only has two stage filtration so the HEPA is apt to get clogged more quickly. If you use it as a wet vac, you don't use the filter bag so it becomes a one stage filter and you might go through HEPA cartridges faster than you would like. The filter bags are more expensive than some, but are quite wonderful and include a very nicely designed filter lock to minimize contamination while changing and disposing of the bag.
[A note about WAP. When Batyah and I contacted WAP's American wholesale distributor, we were told, on more than one occasion, that their HEPA vacuum sold for $1,245. I can't figure out why we were told this as our local retailer priced the SQ10, with the HEPA filter, for about $835.]
HEPA versus ULPA. I do have an opinion. HEPA is the legal standard for lead dust and asbestos mitigation. For those tasks it is more than adequate. (ULPA is legal, too.) However, if you are cleaning up something with an even smaller particle size, then you should use an ULPA filtered machine.
Some of the hazardous materials that conservators use that are very fine particulates include powdered organic dyes, condensed lead fumes (around molten lead or leaded bronze), or very finely divided modern pigments like the cadmiums. In all of these cases, you are even safer with a ULPA filter protecting your breathing space.
When is a HEPA not a HEPA? When the hospital lobby sets the specification. Avoid hospital-grade HEPA, HEPA-like, or Gore-Tex microfilters. These are cheaper (the hospital lobby's interest) but in spite of similar looking ratings, not acceptable for conservation work.
1 Steven Waldmand, et al., "Lead and your Kids," Newsweek, July 15, 1991, pp. 42-48.
2 "Lead from Mothers' Bones Transfers to Fetus", ACTS FACTS, ed. Monona Rossol, Vol. 10, No. 9, September 1996, p. 3.
3 Marian Burros, "Eating Well: Testing Calcium Supplements for Lead," The New York Times, Wednesday, June 4, 1997, Section C.
4 Donald B. Louria, "Section 565. Trace Metal Poisoning" in "Occupational and Environmental Medicine", pp. 2307-2309.
Special thanks to Susan Lambert, Lis Barfod, and Monona Rossol.
Chris Stavroudis is a conservator in private practice.