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Feature Vol. 59, No.7, p. 12-17

Public Health and Environmental Benefits
of Adopting Lead-Free Solders

Oladele A. Ogunseitan

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Figure 1
Potential for human exposure to toxic lead occurs throughout the life cycle from mining to metal production, product manufacture, and end-of-life disposal. In the U.S. limits on occupational exposures are established by the Occupational Safety and Health Administration; whereas the U.S. Environmental Protection Agency is responsible for setting the limits on public and ecological exposures.




Figure 2
Regional disparities in lead mining, metal production, and lead consumption, which likely reflect disparities in health risks associated with human exposure to lead.




Figure 3
Timeline for legislative initiatives and implementation to restrict the use of lead and other toxic materials in electrical and electronic products in different parts of the world. The main top arrow describes the situation in the European Union. The bottom main arrow describes the situation in Asia and the United States, where only California has a comparable regulation on recycling and sales of products containing unacceptable levels of lead.
















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Editor’s Note: Sustainability in electronics will be the topic of a webinar on September 27, hosted by the author of this article and co-sponsored by TMS. For more information visit

After more than 7,000 years of widespread use, lead is figuratively sinking in contemporary industrial ecology and global societal commerce. But, despite the long research history of documenting the detrimental impacts of lead use, and of legislative initiatives to phase lead out of various products and processes, the United States currently has no federal mandate comparable to the European Union’s “restriction of the use of certain hazardous substances in electrical and electronic equipment” banning the sale of new electrical and electronic equipment containing specified levels of six major toxic materials, including lead. Without a strong environmental agenda leaning toward preventive strategies, concerns about demonstrated public health effects often prove to be strong motivators of U.S. materials use policy. This article assesses various ways in which universal adoption of lead-free solders, coupled with additional material restrictions, may have tangible benefits for public health and the environment, and how these benefits may help secure true innovation in material selection and product design for the environment.


The Latin word for lead, plumbum, may have derived from the original Sanskrit bahu-mala, meaning “very dirty.”1 Throughout recorded history, lead has been known to be toxic. H.L. Needleman2,3 points out that evidence of lead toxicity existed in 2000 b.c. Having been phased out of Western civilization’s staples such as gasoline, paint, and water distribution pipelines, the elimination of lead in electronic products is imminent. The toxic metal’s last major refuge is automobile batteries which demand more than 70% of global lead assets but are largely recycled with notable fugitive emissions that contaminate the environment worldwide.4 The events leading to various legislative initiatives to eliminate lead from electronic products are based on its notorious legacy as a major health hazard across the spectrum of human generations and cultures.5 However, there are concerns about anchoring industrial product design and innovation on legislative mandates that specify the elimination of one chemical without providing rigorous guidelines about the selection of alternatives which should, in principle, be less toxic, perhaps cheaper, and certainly function properly in the manufacturing process in which they are embedded.3 The health effects of human exposure to lead are better understood than any potentially viable replacement. As such, more research is needed to document the implications of phasing lead out of solder materials and the likely impacts of the replacement for human health and the environment throughout the life cycle of the materials.

Human exposure to lead occurs at various stages of production and use as depicted in Figure 1. Mining of galena (lead sulfide) represents the origin of the life-cycle assessment (LCA) of lead, and this stage has one of the most profound lasting impacts on environmental quality and human health.6,7 Figure 28 presents data on the trend of lead mining, metal production, and consumption worldwide. Clearly, there are some notable regional disparities in these activities that are likely to translate to differences in occupational health risks associated with mining, metal works, and product life cycle. The Asia region has dominated lead mining, production, and consumption in recent years, and the demand for lead in that region is growing. The Americas exhibit a slight decline in lead mine production, although the United States harbors some of the strongest legacies of the adverse effects of lead mining. Among the best documented public health effects of lead mines are associated with the U.S. Environmental Protection Agency (EPA) Superfund site at Coeur d’Alene river basin in northern Idaho. The average blood lead level (BLL) of children ages 1 through 5 in the region is 2–3 μg/dL higher than the national average, and up until the year 2000, more than 15% of the children had BLL > 10 μg/dL (compared to the national average of 2%), which is the action level recommended by the United States Centers for Disease Control.6

Table I.
Health Effects or Physiological Changes Associated with Blood Lead Levels9
Blood Lead Levels (μg/dL)
Health Impacts Children Adults
IQ Reduction (1–4 points, mean of 2.6)a 10–20 N/A
IQ Reduction (2–5 points, mean of 3.5)a 20 N/A
Increased Systolic Blood Pressure (1.25 mm Hg) N/A 10-15b
Increased Systolic Blood Pressure (2.50 mm Hg) N/A 15-20b
Increased Systolic Blood Pressure (3.75 mm Hg) N/A Above 20b
Gastrointestinal Effects 60 N/A
Anemia 70 80
Nephropathy 80 120
Encephalopathy 90 140
aIn children aged 0–1 only; bin men, aged 20–79; NA = not applicable, or data not available.

Cognitive deficits or mild mental retardation are the most insidious health hazards associated with lead exposure in vulnerable children, where a BLL between 10 μg/dL and 20 μg/dL is associated with up to 4 points reduction in intelligence quotient. In adults, hypertension, anemia, kidney disease, gastrointestinal disorders, and brain damage are all documented health hazards associated with untreated lead poisoning (Table I).9 Despite the introduction of various legislative initiatives to limit the use of lead in several industries (see Table II), most people still have measurable BLL which is typically less than 5 μg/dL in the United States, a positive outcome of phasing lead out of gasoline. Exposure of the general population to lead comes from various sources, and it is difficult to apportion a specific level of risk of lead exposure to its use in solder materials. However, the legacy of “hot spots” including old mines, fugitive releases from industries, and occupational exposures may account for most of the current levels of lead exposure. According to the U.S. EPA’s Toxic Release Inventory program, 8.47 million kg of metallic lead was reported by U.S. industries in 2005, in addition to 204.38 million kg of lead compounds, making a total of 212.86 million kg for that year.10 Additional information on the sources of lead in the environment can also be derived from the amount of lead used by the major industrial sectors. In 2005, 1.46 Mt of lead was used in the United States, with 88% going to storage batteries and 4.2% going to ammunition, the largest two categories. The U.S. Geological Survey does not routinely disclose the amount of lead used by electrical and electronic manufacturing industries (SIC code 36) to avoid disclosing company proprietary data.11


Given the legacy of lead as a pervasive environmental pollutant and the potency of its health impacts, it is not surprising that jurisdictions across the world have tried to limit its use. The current drive to eliminate lead from solder materials began with concern over water distribution systems where direct population exposure to lead from potable water was demonstrated (Table II). Subsequently, the European Parliament and the Council of the European Union (EU) on January 23, 2003 adopted directive 2002/95/EC on the restriction of the use of certain hazardous substances in electrical and electronic equipment (restriction of the use of certain hazardous substances in electrical and electronic equipment [RoHS], Figure 3). The directive covered a broad range of uses for toxic chemicals, with three articles specifically addressing lead, as shown in the sidebar.

Table II.
The Fate of Legislative Initiatives to Reduce Lead Use across Various Industrial Sectors in the United States
N. American Industrial Classification Systems Codes Products Pb Component Regulartory Program Replacement/ Alternative Policy Remarks
32411 Petrochemical refining Tetraethyl Pb additive National phase-out 1975-1987 Manganese (MMT); MTBE Incomplete global phase-out of Pb; uncertainty about health and ecological impacts of alternatives
335911 Storage batteries Pb electrodes State regulated recycling programs “Green batteries” nickel-metal hydride Voluntary programs, incentives
331511 / 326220 Water piping   National phase out June 1986-June 1988 “Pb-free” pipes and fittings (8% Pb); “Pb-free solder” (0.2% Pb) Fixtures, old tanks remain hazardous for next decade
23321 Coloring pigments Pb pigments Residential Pb-Based Paint Hazard Reduction Act of 1992 (PL 102-550) Pb-free pigments Persistent litigation; paint replacement hazards in old buildings
334411 Electron Tubes Pb oxide RoHS/WEEE Flat panels; Hg Premature collection programs. Int'l trade. Uncertainty about Pb leaching conditions
334412 Printed circuit boards Sn-Pb solders RoHS/WEEE Pb-free solder, silver, bismuth, indium Uncertainty about risks of alternatives; costs and benefits of switching

After July 1, 2006, the European RoHS prohibits the sale of electrical and electronic equipment containing the four metals listed in the sidebar and certain brominated flame retardants at the specified concentrations.12 The RoHS directive is expected to work in concert with the Waste Electrical and Electronic Equipment (WEEE) directive (2002/96/EC) to reduce the environmental and human health burden posed by discarded electronic products.13 Specifically, WEEE mandates the producers of electrical and electronic equipment to finance the collection, recycling, or otherwise adopt non-hazardous disposal of their products after consumers are ready to discard them. Although there are some exemptions granted or under review based on the argument that safe and reliable alternatives are not currently available,14 most electronics and electrical equipment manufacturers have been searching and testing for alternative materials for more than a decade. In this regard, much effort has focused on finding alternatives to the ubiquitous time-tested tin-lead solder material.5

Following the impetus of the EU directives, Japan,15 China,16 South Korea,17 and the U.S. state of California18 have instituted similar regulations to limit the use of lead and other RoHS toxicants in electronic and electrical equipment (Figure 3). This convergence of legislative initiatives has increased the geographical scope and pace of activities to redesign electrical and electronic products using lead-free components. The most vulnerable component of electronic products is the printed wiring board, where the use of eutectic tin-lead solder has been traditional. Several alternative lead-free solder materials are now being marketed and used in electronic products, but in the absence of clear guidance on performance reliability, toxicity, and human exposure guidelines in both occupational settings and the open environment, it has been difficult to compare the alternatives to tin-lead solder in terms of potential for human health impacts. Numerous lead-free solders have been produced as replacements. For example, solders made with various combinations of tins, silver, and copper (SnAgCu solders) have been adopted by several Japanese manufacturers for reflow and wave soldering. These include SnAg3.0Cu0.5 with a melting point (m.p.) of 217–220°C; eutectic SnAg3.5Cu0.9 (m.p. 217°C); SnZn9 (m.p. 199°C); SnZn8Bi3 (m.p. 191–198°C); SnSb5 (m.p. 232–240°C); SnAg2.5Cu0.8Sb0.5 (m.p. 217–225°C); SnIn8.0Ag3.5Bi0.5 (m.p. 197–208°C); SnBi57Ag1 (m.p. 137–139°C); and SnIn52 (m.p. 118°C). Whereas annual tests for BLL are required for workers using lead, some of the replacement metals including indium and bismuth have no clearly established occupational exposure standards nor do they have rigorous public health and environmental regulations associated with their disposal (Table III).


Chemicals controlled by the European Union restriction of the use of certain hazardous substances in electrical and electronic equipment regulations are as follows:

  • Mercury in compact fluorescent lamps not exceeding 5 mg per lamp
  • Mercury in straight fluorescent lamps for general purposes not exceeding halophosphate–10 mg; triphosphate with normal lifetime–5 mg; and triphosphate with long lifetime–8 mg
  • Mercury in straight fluorescent lamps for special purposes
  • Mercury in other lamps
  • Lead in glass of cathode ray tubes, electronic components, and fluorescent tubes
  • Lead as an alloying element in steel containing up to 0.35% lead by weight, aluminum containing up to 0.4% lead by weight, and as a copper alloy containing up to 4% lead by weight
  • Lead in high-melting-temperature-type solders (i.e., tin-lead solder alloys containing more than 85% lead), specifically, lead in solders for servers, storage, and storage array systems (exemption granted until 2010); lead in solders for network infrastructure equipment for switching, signaling, transmission, as well as network management for telecommunication; and lead in electronic ceramic parts (e.g., piezoelectronic devices)
  • Cadmium plating except for applications banned under Directive 91/338/EEC amending Directive 76/769/EEC relating to restrictions on the marketing and use of certain dangerous substances and preparations.
  • Hexavalent chromium as an anti-corrosion of the carbon steel cooling system in absorption refrigerators
Even if all electronic products replace tin-lead solder with lead-free solder and abide by the RoHS mandate, recent research indicates that according to California’s hazardous waste classification criteria, most electronic products might still be considered hazardous. This is due to excessive content of copper, nickel, antimony, and zinc.19 Various organic chemicals have also been detected, most of which have no current regulatory restrictions. These observations make it clear that there is room for additional innovation in materials selection and product design to truly make electronic products as free as possible from risks to human health and environmental quality— beyond the requirement of current legislative initiatives. The situation is particularly urgent because of a trade imbalance that has created a huge market for used and defunct electronic products in developing countries. Without a well-developed recycling and refurbishing program in developed countries, we can expect that health risks associated with outmoded electronic products will continue to be shifted from one part of the world to another.20,21 Human exposure to lead from electronic products is more problematic because of illegitimate recycling in cottage industries in developing countries that have little or no regulatory oversight.22

International movement of hazardous products containing lead is under the regulatory control of The Basel Convention on the control of transboundary movements of hazardous wastes and their disposal.23 The convention entered into force on May 5, 1992, and as of May 22, 2006, 169 countries have ratified it. Unfortunately, the United States, a major source of potentially hazardous electronic waste, signed in 1990, but has yet to ratify the convention. Instead, on March 13 1996, the U.S. government communicated the following caveats to the United Nations secretariat regarding the Basel Convention:
  1. “It is the understanding of the United States of America that, as the Convention does not apply to vessels and aircraft that are entitled to sovereign immunity under international law, in particular to any warship, naval auxiliary, and other vessels or aircraft owned or operated by a State and in use on government, non-commercial service, each State shall ensure that such vessels or aircraft act in a manner consistent with this Convention, so far as is practicable and reasonable, by adopting appropriate measures that do not impair the operations or operational capabilities of sovereign immune vessels.
  2. It is the understanding of the United States of America that a State is a ‘Transit State’ within the meaning of the Convention only if wastes are moved, or are planned to be moved, through its inland waterways, inland waters, or land territory.
  3. It is the understanding of the United States of America that an exporting State may decide that it lacks the capacity to dispose of wastes in an ‘environmentally sound and efficient manner’ if disposal in the importing country would be both environmentally sound and economically efficient.
  4. It is the understanding of the United States of America that article 9 (2) does not create obligations for the exporting State with regard to cleanup, beyond taking such wastes back or otherwise disposing of them in accordance with the Convention. Further obligations may be determined by the parties pursuant to article 12. Further, at the time the United States of America deposits its instrument of ratification of the Basel Convention, the United States will formally object to the declaration of any State which asserts the right to require its prior permission or authorization for the passage of vessels transporting hazardous wastes while exercising, under international law, its right of innocent passage through the territorial sea or freedom of navigation in an exclusive economic zone.”
Consequently, it seems certain that health risks associated with lead-containing waste electronic products will continue to flow from the United States to other countries, particularly because the United States does not have a national legislation similar to RoHS or WEEE to restrict the sales of lead-containing products. Instead of the piecemeal approach to restricting the disposal of certain hazardous waste materials into landfills, a comprehensive review of the bill of materials in high-volume products such as cell phones needs to be conducted in order to target the most toxic components for replacements. The United States should also initiate discussion across states on uniform policies of material restrictions that will not be confusing for manufacturers and consumers.

Table III. Comparative Assessment of Environmental
and Health Standards for Metal Use in Solders

Permitted Exposure Level, 8 hour-TWA** 15 mg/m3 0.01 mg/m3h 5 (respirable fraction)– 15 (total dust) mg/m3h 0.1 (fume)– 1.0 (dust) mg/m3h 0.1 mg/m3h 2 (inorganic),0.1 (organic); 5 (respirable fraction) –15 (total tin oxide dust) mg/m3h
Threshold Limit Value*** (mg/m3) 0.15 0.1 0.2 mg (Se)/m3 for bismuth selenide; 10 mg/m3 for bismuth telluride 0.1 0.1 2.0
Total Maximum Daily Load (Number of Impairments) 480 47 No monitoring program 510 No monitoring program No monitoring program
Maximum Contaminant Level in H2O Zero 0.1 mg/L No established standard 1.3 mg/L No established standard No established standard
Toxic Release Inventory**** 8.2 (Pb) 170 (Compounds) 0 04 (Ag) 2.1 (Compounds) No monitoring program 10 (Cu) 630 (Compounds) No monitoring program No monitoring program
Health Impairment Levels Blood lead level in children = 10 mg/100 g Oral reference dose = 0.005 mg/kg/day Man, unreported route: LDLO:221mg/kg; Oral, Rat: LD50: 5g/kg Liver storage; 500 mg/kg Not established. Indium 111 – in cancer therapy Not established standard.
Toxicity Symptoms Cognitive and development impairment in children; hypertension argyria or permanent skin discoloration; tissue degeneration "Tellurium breath;" foul breath and stomatitis; malaise, nausea, and depression Gastro-intestinal ailment; kidney and liver failure No established standard Disturbance of immune function; psychosis

* Bismuth telluride; undoped.
** Occupational Safety and Health Administration.
*** American Conference of Government Industrial Hygienists.
**** National data for year 2000 in million kg.


As part of a major programmatic initiative, the U.S. National Science Foundation (NSF) launched an interdisciplinary research agenda titled “biocomplexity in the environment” (BE). Biocomplexity refers to “the dynamic web of often surprising interrelationships that arise when components of the global ecosystem—biological, physical, chemical, and the human dimension—interact.” Projects supported by the BE program aim to provide comprehensive understanding of natural cycles and processes, the reciprocal effects of human behaviors and decisions on natural phenomena, and the ways in which technological innovation can mediate the interface between society and nature in a sustainable way.24 Clearly, the selection and combination of different kinds of materials used in various products play a central role in understanding biocomplexity. Therefore, the NSF created a sub-program under BE entitled “Material Use: Science, Engineering and Society” (MUSES) that is focused on integrating multidisciplinary research in engineering, natural sciences, social and behavioral sciences, economics, mathematics, and education to address complex issues related to materials use in the environment.25

Various academic traditions have attempted to capture the spirit of MUSES for some time. The oldest and most successful of these is “Human Ecology,” which deals with the interactions between humans and their natural, social, and artificial environments. Human ecology is a multidisciplinary endeavor, although it has been more closely identified with the social sciences. Generations of scholars have made their careers in human ecology, and there is at least one major scholarly journal.26 An attempt to integrate environmental policy, political systems, and behavior more closely with human ecology to make it an active rather than descriptive endeavor led to the creation of another multidisciplinary program called “Social Ecology.” The boundaries between human ecology and social ecology are permeable, but there is an Institute of Social Ecology, which published “Harbinger: a journal of social ecology.”27 In the early 1990s, a more focused conceptual framework to analyze the relationships between human and natural systems emerged through the definition of “Industrial Ecology,” which attempted to model industrial systems to fit more closely with natural ecosystems that are essentially closed systems with the input of energy from the sun, and no waste products. Industrial ecology deliberately incorporates an international dimension to the understanding of human and social ecology, and it is perhaps more analytical than philosophical in its orientation. There is a strong methodological framework heavily invested in materials life-cycle assessments. There is a training component nurtured by the International Society for Industrial Ecology,28 and there is a Journal of Industrial Ecology published by MIT Press.29

All these academic traditions approach the same urgent question through different pathways: how do we find innovative solutions to environmental problems without compromising economic productivity and human and ecological well being? The issue of lead-free solders is an excellent example of a challenging problem for society, regardless of whether you approach it as a human ecologist, a social ecologist, an industrial ecologist, or simply as a materials scientist.


Research in the author’s laboratory is supported in part by grants from the National Science Foundation (DMI- 0223894 and CMS-0524903) and by an interdisciplinary research award TS-30856 from the University of California Toxic Substances Research and Teaching Program. Additional support was provided by the Program in Industrial Ecology at the University of California-Irvine. I thank my colleagues, Jean-Daniel Saphores, Julie Schoenung, Andrew Shapiro, and our students and postdoctoral researchers for helpful discussions on this project.


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Oladele A. Ogunseitan, Professor of Public Health and Professor of Social Ecology, Director, Industrial Ecology Research Group, University of California, Irvine, CA 92697-7070 USA; (949) 824-6350; fax (949) 824-2056; e-mail