Alternatives for significant uses of lead in Massachusetts
In July 2005, the Commonwealth of Massachusetts requested that the Toxics Use Reduction Institute perform an alternatives assessment for five chemicals. For each chemical, the Institute was charged with identifying significant uses in manufacturing, consumer products, and other applications; reviewing health and environmental effects; and evaluating possible alternatives. The results of this study will serve as a guide for those seeking safer substitutes to the five chemicals discussed here.
Presented here is an executive summary of the findings of for high priority uses of lead in Massachusetts. The full report, the Five Chemicals Alternatives Assessment Study available from the link below, presents extensive factual information on each alternative.
Lead and lead compounds
Lead is a naturally occurring metal with a high density and low melting point. It is ubiquitous in manufactured products in many forms: as a pure metal, as an alloy with other metals, and in compounds. It is valued for its electrical conductivity, high density, and ability to stabilize plastics.
Lead poses a serious threat to human health and the environment. Acute human health effects of high lead exposures can include gastrointestinal distress, brain and kidney damage, and death. Chronic effects of lead exposure include anemia, damage to the nervous system, effects on blood pressure and kidney function, and interference with vitamin D metabolism. The U.S. Environmental Protection Agency (EPA) has classified lead as a probable human carcinogen, and the International Agency for Research on Cancer (IARC) has classified inorganic lead as probably carcinogenic to humans (Group 2A). Fetuses, infants and children are particularly vulnerable to adverse effects from lead exposure, including irreversible neurological damage. There is no known safe threshold for lead exposure in children.
Lead is extremely persistent in both water and soil. Combustion of leaded gasoline was a major source of anthropogenic lead releases in the past. Industrial releases from smelters, battery plants, chemical plants, and disturbance of older structures containing lead-based paints are now major contributors to total lead releases. The Institute selected three priority uses of lead to assess in detail: ammunition, weighting applications, and heat stabilizers for PVC wire and cable coatings. These applications were chosen based on stakeholder interest, importance to Massachusetts industry and consumers, and likely availability of alternatives. Ammunition used at indoor and outdoor firing ranges is a significant source of occupational lead exposure and environmental contamination. Automotive wheel weights and fishing sinkers were chosen as representative of a large number of lead uses that rely on its high density. Wire and cable heat stabilization is the category with the largest use of lead among Massachusetts manufacturers. The results of these assessments are summarized below.
Ammunition for shooting ranges
Most practice shooting ranges currently use lead ammunition. Range operators and shooters can be exposed to high airborne lead levels in indoor shooting ranges. Use of lead ammunition at outdoor shooting ranges can produce environmental contamination. Most of the major ammunition manufacturers now market lead-free bullets. A few smaller ammunition manufacturers specialize in the production of lead-free ammunition.
The Institute examined five possible alternatives to lead ammunition for use in shooting ranges: bismuth, copper, iron, tungsten, and zinc. For each alternative, the Institute examined human health, environmental, technical, and cost criteria.
- Human health. The alternative materials are all superior to lead from a human health perspective for the criteria the Institute considered (carcinogenicity, developmental toxicity, and occupational exposure).
- Environment. In general, the alternatives are more desirable from an environmental standpoint, with the exception of aquatic toxicity for copper and zinc.
- Technical criteria. Technical criteria of interest for this application include density, frangibility, and barrel wear.
- Greater bullet density is advantageous for most ammunition applications, since high bullet weight and small bullet size are both desired characteristics. Tungsten has greater density than lead, while the other alternatives have lower density than lead. However, the density of bismuth is very close to that of lead. One manufacturer produces bismuth bullets that match the weight of many lead bullets.
- Many lead-free bullets are frangible, which means they fragment into small particles upon impact with a target. Frangible bullets are safer than lead bullets for use at indoor firing ranges because they reduce or eliminate the dangers associated with ricocheting bullet fragments. This is of particular concern when firing at steel targets at close range. Frangible bullets can also limit damage to steel targets. Bismuth, iron, tungsten/nylon, and powdered copper can all be used to make frangible bullets. Solid copper bullets are not frangible and may ricochet more readily than lead bullets. Some zinc bullets break apart upon entering a target, but their probability of ricochet is not known.
- Barrel wear is the erosion of barrel material by bullets. All of the alternative materials except tungsten are similar to lead from the perspective of barrel wear.
- Cost. All the alternatives currently have a higher purchase price than lead bullets. However, all the alternatives are superior to lead bullets from the perspective of operating costs. Firing ranges face numerous costs associated with the use of lead ammunition. These can include costs of air monitoring, blood lead level testing of range operators, maintenance of containment and filtration systems, purchase of replacement filters, range cleaning, and lead disposal. By switching to lead-free ammunition, firing ranges can reduce or eliminate costs in these areas. In addition, lead bullets and bullet fragments must be either recycled or disposed of as hazardous waste. Alternative bullets, in contrast, can be disposed of as non-hazardous waste if they are not recycled. Frangible bullets also reduce wear and damage on bullet traps and backstops.
The Institute chose wheel weights and fishing tackle as two examples of the larger category of lead used in weighting applications.
Nearly 2,500 metric tons of lead are used each year in the United States to produce fishing sinkers. Many of these sinkers are lost during use. One study found that anglers lost, on average, one sinker every six hours of fishing. Lead sinkers are lethal to waterbirds, such as loons and swans. One study found that the most common cause of death in adult breeding loons was lead toxicity from ingested fishing sinkers. A number of states have placed limits on the use of lead fishing sinkers. In Massachusetts, lead sinkers are prohibited for use in the Quabbin and Wachusett Reservoirs, the two bodies of water that support the core of the state's loon population. Use of lead sinkers is restricted in several other states in the Northeast, and is restricted or banned in several countries. Many anglers produce their own lead sinkers at home. This activity can expose individuals and family members to airborne lead particles or vapors.
The Institute examined five possible alternatives to lead for use in fishing sinkers: bismuth, ceramic, steel, tin, and tungsten. For each alternative, the Institute examined human health, environmental, technical/performance, and cost criteria.
- Human health. All the alternative materials are superior to lead from the perspective of the human health criteria the Institute examined (carcinogenicity, developmental toxicity, and occupational exposure).
- Environment. The alternatives are generally superior to lead from an environmental standpoint as well. All of the alternatives are clearly less hazardous to waterfowl and other aquatic species than lead.
- Technical criteria. The principal technical criteria of interest for this application are density, hardness, malleability, melting point, and corrosion resistance.
- Tungsten is more dense than lead; all the other alternatives are less dense than lead.
- Harder materials are preferable for use in many sinkers. All the alternatives are harder than lead; pure tin is about equal to lead in hardness, while tin alloy is harder than lead.
- Greater malleability is an advantage for sinker applications where the sinker is crimped on to the fishing line. Tin has malleability equal to that of lead; all of the other alternatives are less malleable than lead.
- Low melting point is considered an advantage because it allows individuals to produce sinkers at home, although home production of lead sinkers also creates human health hazards. Bismuth and tin have lower melting points than lead; ceramic, steel, and tungsten have higher melting points.
- Carbon steel is less resistant to corrosion than lead. Stainless steel and all the other alternatives are similar to lead in this regard.
- Cost. The alternatives generally have a higher retail price than lead sinkers, although some steel sinkers are competitive in price with lead sinkers. Studies conducted in the 1990s suggested that fishing sinker purchases represent less than 1% of total expenditures by anglers on their sport, so an increase in fishing sinker costs would be unlikely to have a significant effect on users.
Wheel weights often fall off automobile wheels, leading to lead contamination of the environment. Worker exposure is a concern in the installation of wheel weights.
There is a thriving market in lead-free wheel weights. European and Japanese automobile manufacturers have already switched to lead-free wheel weights and U.S. automobile manufacturers are currently in the process of making the switch. Asian auto manufacturers now primarily use steel weights. Zinc weights are used widely in Europe, and US auto manufacturers are using zinc weights for automobiles destined for export to Europe. General Motors and Ford are in the process of converting to steel weights.
Despite these developments, the U.S. market in replacement wheel weights continues to use lead weights almost exclusively. This market in replacement weights accounts for 80% of total wheel weight use in the U.S.
The Institute examined four possible alternatives to lead wheel weights: copper, steel, tin, and zinc. For each alternative, the Institute examined human health, environmental, technical/performance, and cost criteria.
- Human health. All of the alternative materials are superior to lead for the human health criteria the Institute examined (carcinogenicity, developmental toxicity, and occupational exposure).
- Environment. For the most part the alternatives are superior environmentally, although zinc is inferior for aquatic toxicity in salt water, and copper is inferior for aquatic toxicity in both fresh and salt water.
- Technical criteria. The principal technical criteria of interest for this application are density, malleability, and corrosion resistance.
- All of the materials considered in this analysis are less dense than lead. Thus, in order to achieve the same mass, the weights made from alternative materials must be somewhat larger than their lead counterparts. This adjustment does not typically pose engineering difficulties for weights used on passenger vehicles.
- The malleability of lead makes it possible to shape wheel weights to match the curve of the wheel diameter. The malleability of copper and tin is similar to that of lead; steel and zinc are less malleable. Manufacturers can compensate for lower malleability by creating segmented weights.
- The corrosion resistance of the alternative materials is generally similar to that of lead; tin is superior to lead in this regard because it does not require coating.
- Cost. Copper and tin weights are expected to cost more than lead weights at initial purchase; zinc weights cost about the same as lead weights, and steel weights have equal or lower cost. The end of life costs for all the alternatives are lower than those for lead.
Heat stabilizers for PVC wire and cable coatings
Lead heat stabilizers used for polyvinyl chloride (PVC) constitute the largest use of lead compounds in Massachusetts manufacturing, and the wire and cable industry is the largest user of these compounded resins.
Significant progress has been made in the identification and adoption of alternatives. Many lead-free heat stabilizers are commercially available, and resin compounders are working proactively with wire and cable companies to encourage their adoption. Regulatory requirements prohibiting the use of lead and other hazardous substances in electrical and electronic equipment in the European Union have created an incentive for U.S. manufacturers to develop lead-free alternatives. The Institute is engaged in on-going collaborative projects to help Massachusetts industries to gain and maintain a competitive edge in producing lead-free wire and cable, as well as lead-free electrical and electronic equipment.
The Institute did not conduct a complete technical assessment for alternative heat stabilizers. Each application has unique technical requirements, and stabilizers are formulated with many different combinations of chemicals to suit each application. Furthermore, heat stabilizers will be examined as part of a collaborative project between the Institute and the U.S. EPA to conduct a detailed life cycle assessment for three specific wire and cable applications. However, many Massachusetts wire and cable companies plan to adopt lead-free alternatives before that study will be complete. Thus, stakeholders determined that it would be useful for the Institute to analyze the environmental health and safety profiles of chemicals that are widely used in alternative stabilizers.
The Institute gathered information on five categories of alternative heat stabilizers: calcium-zinc, barium-zinc, magnesium-zinc, magnesium aluminum hydroxide carbonate hydrate, and magnesium zinc aluminum hydroxide carbonate. From these categories, the Institute selected five representative heat stabilizer products and conducted an environmental health and safety assessment of their constituent materials. Many of these constituent materials were found to be superior to lead from a human health and environmental perspective. Costs of mixed metal heat stabilizers have decreased in recent years, such that a transition to a mixed metal heat stabilizer may be cost neutral. Where a cost differential exists, it is estimated at 10% or less.
- For a full report on this and other chemicals see the TURI Five Chemical Alternatives Assessment Study