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You know lead is toxic, but do you know what makes it poisonous? In a nutshell, it's toxic mainly because it preferentially replaces other metals (e.g., zinc, calcium and iron) in biochemical reactions. Lead interferes with the proteins that cause certain genes to turn on and off by displacing other metals in the molecules. This changes the shape of the protein molecule such that it can't perform its function. Research is ongoing to identify which molecules bind with lead. Some of the proteins that are known to be affected by lead regulate blood pressure (which can cause development delays in children and high blood pressure in adults), heme production (which can lead to anemia), and sperm production (possibly implicating lead in infertility). Lead displaces calcium in the reactions that transmit electrical impulses in the brain, which is another way of saying it diminishes your ability to think or recall information, or makes you stupid.
Paracelsus' idea that the dose makes the poison doesn't really apply with lead. Many substances are non-toxic or even essential in trace amounts, yet poisonous in quantity. You need iron to transport oxygen in your red blood cells, yet too much iron can kill you. You breathe oxygen, yet again, too much is lethal. Lead isn't like those elements. It's simply poisonous. The main concern is lead exposure with small children, because lead can cause developmental problems, plus kids engage in activities that increase their exposure to the metal (e.g., putting things in their mouths, not washing their hands). There is no minimum safe exposure limit, in part because lead accumulates in the body. There are government regulations regarding 'acceptable' limits for products and pollution, because lead is useful and necessary, but the reality is, any lead is too much lead.
Photo: Lead bricks may be used as radiation shielding. (L. Chang, wikipedia.org)
Comments
i loved id it was so detailed frome annie
uhm yes.
where was this research taken place?
Uh, follow the link in the article for where the research was done?! http://chemgroups.northwestern.edu/godwin/research.htm
A minor (but happy note) is that most commercial uses of lead-based solders in manufactured electronics have nearly been eliminated. This also includes “coatings” mentioned. This is good for recycling/disposal of the current generation of electronics.
If you order electronic parts of any type now (say from Newark Electronics) you’ll be hard pressed to find “lead solder” versions (that is those that either use lead for contact “tinning” or that have contact surfaces optimized for lead solder or that simple use leaded solder in their manufacture. Instead most parts are now “RoHS compliant” meaning they are designed, manufactured as or made for lead-free solders.
http://www.newark.com/jsp/bespoke/popup.jsp?bespokepage=newark/en_US/rohs_statement.jsp
My own personal experience for leaded and lead-free solders is that leaded solders are still much easier to work with though I try to avoid them for political and humanitarian reasons.
Lead-free solders have three features that make them harder to use: they melt at higher temperatures, they “wet” metal surfaces poorly compared to lead solders, and they have a much higher surface tension when melted. The latter means they form more highly convex meniscuses (they “ball up” more) which causes surface mount parts to “tombstone” more easily. Combined with poor wetting and higher melting point you have a much better chance of damaging parts when you hand solder a project. It takes practice and a more expensive soldering station to get results as good as leaded solder.
I still advise folks doing electronics to try to use lead-free if possible despite these problems. Eventually you won’t be able to buy lead solder at all so why not get good with lead-free asap.
As a side-note, it’s also difficult to still find “mercury-wetted Reed relays” for the obvious reason. Sadly there is not performance-equivalent replacement for these. This means that equipment that would normally be spec-ed to use them must use inferior non-mercury switches which have much shorter lifespans which results in system or component replacements far sooner. The added disposal burden probably obviates the benefits of banning mercury-wetted switches but environmental laws tend not to allow nuanced application because they are usually written by people who have zero-clue about economics, technology and mathematics.
Who say any amount of lead is poisonous. PC garbage.
I was recently listening to a Bill Bryson audio book and he did a section on Thomas Midgley and Clair Patterson. I found it facinating. I have worked with lead everyday since technical college. I am a plumber by trade and inhale lead fumes and physically come into contact with lead every day. I can not see lead being withdrawn from solder as Jeff says leaded solder is far better to work with. Lead as a roofing material is still widely used in Great Britain. i don’t think lead is going to go away. Anne Marie is of course correct. Any lead is too much lead. I enjoyed the article especially the protein bits. Oh by the way I have heard several different people say that the Romans even deliberately put lead in their wine as a sweetener. This includes the Bill Bryson audio book.
Paul
Aquamaster
i think that sure it is dangerous if injested or handled without proper equipment but since george bush and the supreme court gave the EPA the right to ban or regulate anything deemed dangerous, that basically they are sidestepping our constitution and the legislative branch of our government, to make it more expensive to hunt, shoot and fish, if they pass this propossed new regulation. basically to save the lead for their green batteries and to disarm people by putting ammo outta reach by cost. think about it we are the only nation where the citizens can be armed! god bless us all.