Monona Rossol on wed 4 jun 97
From: Kris Baum
Subject: Manganese Toxicity
--------------------------Original message----------------------------
> Sorry to revive such an old thread, but I was able to get some
> information from a nutritionist about manganese that may be of interest
> to those of us concerned about it leaching from our glazes.
> The National Academy of Sciences, National Research Council (not
> a federal govt. agency but an independent agency that does work for the
> govt. under contract) is responsible for setting the Recommended Dietary
> Allowances (RDAs). I believe that the latest report was done quite a
> while ago (maybe 10 years?) and that an update of the RDAs is due in the
> next couple of years.<
**FDA reveiwed the information, changed the name from RDA to RDI (Recommended
Dietary Indices) and amended its nutrition labeling regulations on December
28, 1995 establishing an RDI for manganese.
> The text of the NRC's report makes some of the following points:
> There is no tendency for an increase or decrease in accumulation
> of manganese through most of the human life cycle. This is thought to be
> a result of adequate dietary intake coupled with strong homeostatic
> control (for those non-biologists, this means that the body somehow
> manages to keep a balanced level. In pregnancy, the body increases
> absorption; if overconsumed, it is probably excreted through the stool.)
>
> In humans, the only manganese toxicity has been observed with
> high concentrations of manganese dust or fumes in the air. Dietary
> intake of as high as 9 mg/day has shown no toxicity. "In view of the
> remarkably steady tissue concentrations of manganese in the U.S.
> population and the low toxicity of dietary manganese, an occasional
> intake of 10 mg/day by adults can be considered safe. To include an
> extra margin of safety, however, the subcommittee recommends a range of
> manganese intake from 2 to 5 mg/day for adults."<
The current RDI is set at 2 mg/day. And tissue concentrations may not be
very steady in the US population now--see below.
> In animals, the toxicity of ingested manganese doesn't appear
> until about 1000ug/g of diet are fed. As in humans, the dust is much
> more toxic, resulting in adverse effects on the central nervous system.<
> IMHO, I'll be sure to wear a mask when weighing the stuff out,
> but I'm not going to obsess about the leaching. <
Dear Kris,
I'd obsess about it anyway. We get manganese from a number of dietary and
pollution sources. We don't want to add very much from pottery. 2 mg/day is
not a whole lot. Remember, a standard leach test reads in mg/liter!
And consider that in 1980 when NRC compiled the data, the tests for subtile
neurotoxic effects were not available. In the 1990s we began seeing
associations in humans between very low level manganese exposure and effects
on brain function which in the short term cause memory, coordination, and
psychological symptoms (its hard to ask a rat how he feels) and leads to
Parkinson's like symptoms in later life.
Consider also that the NRC based much of its opinion on the steady tissue
concentrations in the US population. I submit this balance will be more
difficult for us to maintain in the future. Last year, EPA lost
its fight with industry to keep a manganese fuel additive out of US gasoline
as an antiknock ingredient on the basis of its toxicity.
The Canadian Government has allowed this manganese fuel additive in gasoline
since 1977 They now feel there is evidence that it is harmful to the
environment and to human health. The Canadian Government passed a bill to
prohibit importation and interprovincial transport of the manganese fuel
additive. That should have been the end of it, but Ethyl (a corporation
with both US and Canadian branches) filed a $250 million-plus lawsuit
against the Canadian government saying that this action "will severely impact
Ethyl Canada's business, and this is a measure tantamount to expropriation
under NAFTA." (Chris Hicks, Ethyl's VP for government relations.)
Manganese is going to be a very hot button topic for a while. Meanwhile dust
from the old lead-gasoline on the roadsides of both countries is being
replaced with manganese dust. In a decade or two we will have more data on
low level manganese exposure from an experiment in which *we* are the lab
rats.
Monona Rossol, industrial hygienist
Arts, Crafts and Theater Safety
181 Thompson St., # 23
New York, NY 10012-2586 212/777-0062
http/www.caseweb.com/acts/
Kris Baum on thu 5 jun 97
Monona -
Thanks for the more current info. I had gotten the copies of
the RDAs from a nutritionist and they didn't come with full references.
Certainly lots of things eventually turn out more toxic than they
initially appear. Would you please post the info from the 1995 FDA regs?
I think a lot of people on the list would be interested. BTW, I took
back that bottle of vitamins with the manganese!
--
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Kris Baum, Shubunkin Pottery,
mailto:shubunki@erols.com
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