Last week I covered plastics for food
and drink use; this week I'll cover the common metals you might find
or buy for the same purposes. Metal containers have been in use for
thousands of years, but the recent crazes of “detox diets” and
natural-everything have made it hard to find useful information on
the Internet. If a website has “natural” or “health” in the
name and doesn't end in .gov or .edu, take the information found
there with a healthy helping of skepticism.
Metal cans and cups have been around since humans learned how to
work metal. Some metals are safe, some are safe with most liquids,
and some should be avoided at all costs. Starting with the lowest atomic number and working up to end with the common alloys, here are
the more common metals with their pros and cons:
12 Mg- Magnesium
Known for being
light-weight and strong, Mg isn't used for food or water containers
very often. Very reactive and hard to work with due to its low
ignition temperature, Mg is rare in cookware but may be used in a
make-shift water container. Excess Mg is readily excreted from the
body, so only those with certain medical conditions need to worry
about consuming too much.
13 Al- Aluminum
Once a standard
for light-weight cookware and dishes, Al has been linked to
several health issues and is falling out of favor. Al is a very reactive
metal and is always found in combination with another element. Simple
Al oxidizes almost immediately when exposed to air, forming a
protective coating of aluminum oxide, but acidic foods and drinks will
eat through that layer and leach Al into the food/drink. Heat will
also speed up leaching, so cooking in Al will expose you to more.
22 Ti- Titanium
Light, strong, and expensive, Ti is
safe for food use. There is slight chance of being allergic to Ti,
but it is considered non-toxic. I've got a few pieces of Ti holding
bones together, so it's safe to say that it is safe to eat or drink from
containers made of it.
24 Cr- Chromium
A component of most stainless steels,
Cr is also used to plate or cover cheaper metals to give them a
shiny, corrosion resistant covering. Most of the reports of
Crpoisoning are related to ions of Cr used in the plating process and
not the finished product, so using that old chromed hubcap in your water
collection system shouldn't be a problem.
26 Fe- Iron
Required by your body to function, Fe is
non-toxic at all but very high doses. You might have to filter flakes
of rust out of your water, but iron and steel containers are safe to
drink from. Watch for bacteria and other microbes growing in rust and
the pores of iron containers.
28 Ni- Nickel
Like Cr, Ni is used in stainless steel
alloys and as a plating for other metals. Allergic reactions to Ni
are fairly common, so if you can't wear cheap jewelry without
breaking out in a rash you should avoid Ni plated drinking
containers.
29 Cu- Copper
Being easy to work, fairly cheap, and a good
conductor of heat all make Cu a good choice for cookware. It is soft
and scratches easily, so it requires some care. Commonly found in
distilleries and water pipes in old houses, Cu has become more
expensive lately. See Pb, below, for information on solder joints. Cu
is another trace element that your body needs, but high doses should
be avoided.
30 Zn- Zinc
Commonly used to galvanize steel to
give it a rust-proof finish, Zn is a trace mineral needed for proper
bodily functions. Fairly non-toxic, but high doses can interfere with
Fe and Cu metabolism. Avoid heating galvanized steel since doing so
will release toxic fumes. If you are going to use a plated piece of
metal as a grill or pan, make sure you safely burn off the plating
first.
47 Ag- Silver
Solid silver and silver-plated
dinnerware has been around for a long time because not only is it safe to use with food, but it may also have minor antibacterial
properties. I'm not going to get into the colloidal silver debate, but
silver ions have been shown to kill microbes in many lab tests. Too
much in your diet will turn your skin permanently blue-gray
(
Argyria), but it
takes more than that to be toxic.
50 Sn- Tin
Most of us have heard of tin cans,
which are actually steel cans with a thin lining of Tin on the
inside. Tin is a stable metal and not very reactive, so it is less
likely to corrode and contaminate stored food or water than the steel
shell which provides strength. Tin by itself is non-toxic and safe to
use with food and drinks.
79 Au- Gold
Expensive but one of the best for food
contact, gold doesn't tarnish and is almost inert in most
environments, making it very unlikely to contaminate food or water.
82 Pb- Lead
One of the well-known heavy metals that
is hazardous with long-term exposure. Its low melting point makes it
a good solder for joining metals, so it is common in old water
supplies and copper radiators. New potable water supply lines need to
be soldered together with lead-free solder to avoid ingesting Pb with
every cup of water, but such solder is easy to find.
Pb does accumulate in the body, so the
longer you're exposed the more damage it will do to the central
nervous system (CNS), peripheral nerves, kidneys, and circulatory
system. Removing Pb from the body is a delicate procedure requiring
hospital care and chelation therapy. Definitely one to avoid at all
costs!
Alloys
Brass
And alloy of Cu and Zn, brass is a
common decorative metal. It does corrode, as anyone who has ever had
to polish brass buttons on a uniform will attest. Some blends of
brass can contain Pb and there is concern over the possible leaching
of the Pb into water from brass plumbing fixtures. California has
greatly reduced the allowable amount of Pb in all consumer goods, so
newer fixtures should be safer than old ones.
Often used to make musical instruments,
brass has some anti-microbial properties that are being researched.
History shows that brass fittings on ships resist biological fouling,
but until that can be quantified in a lab it is just “anecdotal
evidence”.
Bronze
One part tin and seven parts copper,
bronze is one of the oldest alloys used by man, dating back at
least 5000 years and is still in production today. Large bells and statues
are often made of bronze due to its strength and ease of casting.
Like brass, it can contain trace amounts of Pb as well as other
metals.
Pewter
A blend of Tin, Lead, Copper, and
possibly other metals, pewter is of questionable safety to use with
food. Pewter is used when the maker wants a darker alloy than either
brass or bronze; it is normally gray or brown in color instead of the
reddish-yellow of the other Cu alloys. The presence of any
significant amount of lead would put it far down the list of
potential materials for me.
Stainless Steel
Stainless steel (SS) is a generic name
for a wide variety of alloys of steel and Ni, Mo, Mn, Cr, and a few
other metals. Most common SS alloys are well-suited for use with food
and water, with the only caveat to avoid storing chlorine-based
solutions in SS containers. Chlorine pulls the Chromium out of the
alloy, contaminating the stored liquid and weakening the SS.
As long as you avoid Pb, most metals
are safer to use with food and drink than plastics. They are also
easier to recycle and have a longer usable life than plastics. They
may be heavier, but I prefer metal flasks and cups over plastic.
A side-note on metals and water:
If
you're using a good reverse osmosis (RO) system or a hearty
de-ionization setup, the water coming out may be so clean that it can
actually eat away at metal piping and containers. I've seen this on
an industrial scale and it is possible on smaller sets; copper
contamination in lab-grade pure water that was traced to a repair
made with copper piping on a RO system.
o.
