Letter to My Son About Lead in Machining
Thanks for asking about whether or not lead is a hazardous material. I can understand your curiosity, knowing I worked with lead in the lab, in the melt shop, in the mill where probably 25 percent of our product was leaded steel for machining and in PMPA member company shops when I am asked to help them solve process problems.
In your shop, you probably don’t see a lot of leaded materials, but some shops run almost exclusively on leaded steels, aluminums and brasses. The addition of lead to steel, for example, reduces the amount of power consumed and time required to machine by about 25 to 30 percent. Needing to be competitive in a global market, the reduction in cycle time, improvement in surface finish and the reduction in power needed to make the parts all help our shops be competitive and turn our quotes into orders. Orders that you produce.
The government has regulations that cover the use of lead in our shops, so we could say the government considers it to be a hazard. At the same time, these regulations do not ban its use. If a shop exceeds the quantity of 100 pounds of lead in, “manufacturing, processing or otherwise used in operations,” it must be reported under community right to know and toxic release inventory regulations.
The European Union has a host of regulations that purport to ban or control hazardous materials, and yet most of those that affect the products made by our shops exempt lead. The original 2005 ELV Directive bans lead in Article 4.2(a) “…lead, mercury, cadmium or hexavalent chromium other than in cases listed in Annex II under the conditions specified therein.” But when we go to that Annex II, it exempts lead for machining purposes in steel, aluminum and brass. Here is what the Annex II states:
Lead as an alloying element: 1. Steel for machining purposes and galvanized steel containing up to 0.35 percent lead by weight. 2. a) Aluminum for machining purposes with a lead content up to 2 percent by weight (expires July 1, 2005 per website, current status unknown). b) Aluminum for machining purposes with a lead content up to 1 percent by weight (expires July 1, 2008). 3. Copper alloy containing up to 4 percent lead by weight.
Other European regulations that concern lead include WEEE Directive, which works in concert with RoHS; RoHS (now RoHS II Recast) and others. PMPA has been keeping our members updated on the RoHS recast, and our members got a sneak peek of the June 7, 2016, final report of the study by Oeko-Institut, Fraunhofer and IZM for the Commission, regarding exemption recommendations, which still have not been adopted by the Commission.
In my opinion, the reason lead has not been banned from our work materials is that the environmental advantages leaded materials provide far outweigh the actual human dangers to us on the job. From an environmental point of view, lead as a free machining additive saves between 25 to 30 percent of the energy required to produce suitable parts in steel by machining, so it can be argued that it is more a boon than a bane if we are looking at CO2 emissions (greenhouse gases GHG) deferred. It has no effect on mechanical properties. This is also presuming no one is actually eating the manufactured parts that might contain 0.25 percent of lead added to reduce the energy required to machine the steel. I wrote an article, “Leaded Steels to Protect the Environment,” in “Screw Machine World” Vol 2 No. 4 (July/Aug 2002). In that article, I compared the 10 percent savings on horsepower alone required to more than meet the 7 percent reduction targets of the Kyoto protocols and called lead a winner. Lead in steel for machining saves time, energy and reduces the GHG footprint as it increases your shop efficiency.
From a workplace exposure point of view, in machining shops like ours, where there are no lead vapors or fumes, human pickup of lead is unlikely except through absorption from contact with lead or lead-containing materials. Great hygiene, hand washing before eating, no snacks and no smoking in operating areas, and separate lunchrooms from operating areas are best practices to minimize exposure. Welding or cutting operations that can cause a metal fume provide a pathway for uptake through inhalation and should be assessed for adequate ventilation and exposures monitored. Time of exposure to workers around molten leaded metals is also mandated and monitoring was required in my experience in steelmaking meltshops and continuous casting operations.
The Occupational Safety and Health Administration requires manufacturers to provide a safety data sheet for hazard identification of materials that they produce.
Is this dangerous material? From the current GHS sheet for Leaded Carbon steel bars from Republic Steel:
H302: Don’t eat it. OK.
H372: Harmful through prolonged exposure. Check: What is your exposure? What is the dose? How long?
P260: Don’t breathe in dust or fumes. This is hard to do from a solid piece of barstock.
P264: Wash hands. Check. Not exactly the scariest thing you’ll encounter today.
P270: Don’t eat, drink, or smoke while using this product. This is common sense.
P272: Isolate contaminated work clothing. This makes sense, but again, how is the lead, which is in a solid form in the metal, contaminating the clothing?
Bottom line: Don’t eat it, don’t cut leaded products with a torch and limit exposure time if working around molten leaded metals. Otherwise, remember your lessons from kindergarten and wash your hands, and don’t eat or drink if you aren’t in the lunchroom.
Hope this helps.