Understanding Restriction of Hazardous Substances in Electronics

Table of Contents

• Understanding Restriction of Hazardous Substances in Electronics
• Mercury: Uses and Dangers
  • Mercury in Electronics
  • Toxicity of Mercury
• What is RoHS?
• RoHS and Mercury: A Reduction of Risk
• Mercury-Limiting Legislation

Mercury is restricted by RoHS, but products that are RoHS compliant may still contain mercury in very small quantities. While RoHS compliant does not mean truly mercury free, RoHS works to limit the risks posed by mercury in electronics.

Mercury: Uses and Dangers

While mercury is widely used in a variety of electronic devices, exposure to mercury can be highly toxic.

Mercury in Electronics

Mercury is a heavy metal commonly used in LCD (liquid crystal display) screens. LCD screens use cold-cathode fluorescent lamps (CCFLs) that contain mercury. CCFLs include fluorescent tubes that work to backlight an LCD TV or monitor screen. The light is produced when electricity is used to excite (add energy to) mercury vapor. The vapor is discharged, which creates a fluorescent coating on the inside of the tube that emits light.

Mercury is also used in some laptop screen shutoffs. In a mercury tilt switch used in some laptops, mercury moves to the other side when the laptop is opened or closed. This shift turns the screen on or off.

Mercury was also used to create switches in televisions that were produced before 1991.

Toxicity of Mercury

Mercury exposure at high levels can cause a host of health impacts, including damage to the brain, heart, lungs, kidneys, central nervous system, and immune system. 

Mercury can be released into the air a number of ways, one of which is through burning of electronic products containing mercury. Mercury can be transported in the air for great distances before it is deposited in soil and water.

While mercury exposure is most common by eating seafood containing mercury, exposure to mercury vapor is also possible if an electronic device containing mercury breaks. For example, if an LCD screen containing cold-cathode fluorescent lamps (which contain mercury) breaks, toxic mercury dust or powder can be released.

Mercury can also cause significant environmental damage. When animals are exposed to mercury at high levels, death and reproductive damage can occur.

Read more about mercury in electronics: Mercury

What is RoHS?

RoHS stands for Restriction of Hazardous Substances. The RoHS directive, issued in the European Union, restricts the use of several hazardous materials in electronic and electrical equipment (EEE). All EEE products sold in the EU must comply with RoHS.

RoHS restricts the use of ten hazardous substances in electronics, including mercury. Electronic devices may only contain these substances in amounts lower than 1000 ppm. The allowable amount for cadmium is 100 ppm.

The materials include:

• Cadmium (Cd)
• Mercury (Hg)
• Lead (Pb)
• Hexavalent Chromium (Cr VI)
• Polybrominated Biphenyls (PBB)
• Polybrominated Diphenyl Ethers (PBDE)
• Bis(2-Ethylhexyl) phthalate (DEHP)
• Benzyl butyl phthalate (BBP)
• Dibutyl phthalate (DBP)
• Diisobutyl phthalate (DIBP))

Any manufacturer, importer, or distributor of electronic and electrical equipment (EEE) sold in the EU market must be compliant with RoHS. Before a product is placed on the market, manufacturers must issue a statement declaring that they have taken the proper steps to ensure RoHS compliance. The product is also marked with a CE marking to show consumers the product is RoHS compliant.

EEE regulated under RoHS includes a wide variety of electronic products separated into eleven categories, ranging from large household appliances to medical devices. The eleventh category is all-encompassing, as it includes any EEE not covered in the previous ten categories. 

Read more about how to ensure compliance with RoHS: What is ‘RoHS Compliant’?

RoHS and Mercury: A Reduction of Risk

RoHS works to reduce the risk of mercury exposure by limiting the amount of mercury used in electronic devices. While a product that is RoHS compliant may still contain mercury, it is present in such small quantities that it poses a lower risk if humans are exposed.

Mercury is most toxic at high levels of exposure. Lower amounts of mercury in electronics means there is a smaller chance of high exposure, both for users if a mercury-containing device breaks, and also for manufacturers of mercury-containing devices.

While mercury may still be used in electronics, it is limited to amounts less than 1000ppm. Ppm stands for “parts per million.” In other words, in an electronic device, mercury may only make up .1% or less by weight. This is a fairly small amount of mercury. 

Because of this limit, some manufacturers no longer use mercury. Additionally, RoHS pushes industry to innovate substitutions for restricted hazardous materials. Many manufacturers and scientists are researching alternatives to mercury, such as sulfur hexafluoride. Much research is still needed to truly achieve a mercury substitute.

Mercury-Limiting Legislation

While there is very little legislation that outright bans mercury to create truly “mercury free” products, there is legislation that controls the use, sale, and importation of mercury. This type of legislation works to create more mercury-free products, as mercury is much less widely available and its use comes with more restrictions.

The clearest example of other mercury-limiting legislation is the United States’ Mercury Export Ban of 2008. This legislation works to make mercury less available on the U.S. and international markets in order to reduce the metal’s use in production. Under the ban, export of mercury is prohibited from the U.S. beginning in January 2013. 

Several U.S. states have enacted similar laws to limit the sale of mercury within their state. For example, in 2005, California enacted Assembly Bill 1415 that prohibits the sale of mercury switches. Another example is Connecticut’s 2006 Public Act 06-181, which requires lamps containing mercury to be labeled and bans the use of mercury in button cell phone batteries. Connecticut also enacted phase-out requirements for products containing mercury.

Mercury in electronics is less of a concern than mercury pollution caused by other industries, and mercury pollution is still a problem. A bill introduced in the U.S. Senate in April 2021 aims to create a national mercury monitoring network.

Lead: Restriction of Hazardous Substances in Electronics

Table of Contents

• Lead: Restriction of Hazardous Substances in Electronics
• Properties of Lead
• Lead in Electronics
• Toxicity of Lead
• RoHS: Restriction of Hazardous Substances
  • RoHS Lead Exemptions
• Alternatives to Lead Solder
• Lead-Limiting Legislation

Lead is a heavy metal used in the manufacturing of many electronic devices. Lead’s use is limited by the European Union’s RoHS directive due to its high toxicity.

Properties of Lead

Lead is a heavy metal used in electronics. Heavy metals are metals with relatively high density that are toxic at low concentrations, meaning even a small amount of the metal is toxic. Lead is denser (its particles are more closely packed) than most other materials.

Lead is naturally occurring and is usually found in combination with sulfur in the earth’s crust. The chemical symbol for lead is Pb.

China, the top producer of lead from mines, produced 1.2 million tonnes of lead in 2019, making up almost half of the global total. Australia, Peru, and the U.S. are the other world leaders in production of lead. Each year, more lead is produced from recycled lead-containing materials, rather than from mines.

Characteristics that make lead popular in electronic manufacturing include its softness, its malleability, its ability to be combined with other metals, and the fact that it does not break easily.

Lead in Electronics

Lead is considered one of the most important metals in electronics production. It is most often used in electronics as a compound or alloy with another element.

The main use of lead in electronics is lead soldering. The lead solder attaches two electronic components securely, allowing an electric signal to pass through. For example, lead solder could attach a wire to a circuit board. 

The most common type is tin-lead soldering, which is commonly used in devices where components that are sensitive to heat may crack or melt at high temperatures. When combined with tin, lead has a low melting point, which means it can be worked with at a lower temperature and is less sensitive to variations in temperature. 

Lead is also used in alloys (a mixture) with other metals, such as copper and steel, which expands the use of these metals. Lead alloy in steel is often used in electronic products.

Toxicity of Lead

It is unlikely that the average consumer will experience lead exposure as a result of touching lead solder, as lead solder is used internally in electronics. However, people may be exposed to lead from electronics if a device breaks. More common is lead exposure in workers who manufacture or recycle lead-containing products. Additionally, if lead-containing electronics are put in landfills, as the device breaks down, lead can leach out and contaminate water and soil.

There is no safe exposure level to lead. When lead is swallowed or breathed in, or enters the body another way, it gets stored in blood, which can cause long-term harm.

Lead exposure, particularly in children, can cause damage to the brain and nervous system, lowered IQ, slowed growth, and problems with hearing and speech. Long term exposure in adults can also cause fertility problems, heart disease, and kidney disease.

RoHS: Restriction of Hazardous Substances

RoHS stands for Restriction of Hazardous Substances. The RoHS directive, issued in the European Union, restricts the use of several hazardous materials in electronic and electrical equipment (EEE). All EEE products sold in the EU must comply with RoHS.

RoHS restricts the use of ten hazardous substances in electronics, including lead. Electronic devices may only contain these substances in amounts lower than 1000 ppm. The allowable amount for cadmium is 100 ppm.

The materials include:

• Cadmium (Cd) [The allowable amount for cadmium is 100 ppm.]
• Mercury (Hg)
• Lead (Pb)
• Hexavalent Chromium (Cr VI)
• Polybrominated Biphenyls (PBB)
• Polybrominated Diphenyl Ethers (PBDE)
• Bis(2-Ethylhexyl) phthalate (DEHP)
• Benzyl butyl phthalate (BBP)
• Dibutyl phthalate (DBP)
• Diisobutyl phthalate (DIBP)

Any manufacturer, importer, or distributor of electronic and electrical equipment (EEE) sold on the EU market must be compliant with RoHS. 

EEE regulated under RoHS includes a wide variety of electronic products separated into eleven categories, ranging from large household appliances to medical devices. The eleventh category is all-encompassing, as it includes any EEE not covered in the previous ten categories. 

Read more about how to ensure compliance with RoHS: What is ‘RoHS Compliant’?

RoHS Lead Exemptions

While alternatives to lead soldering exist and are in the process of being refined, exemptions do exist under RoHS for the use of lead in certain applications and electronic categories. These exemptions are given a date upon which they expire, and will no longer be exempt from RoHS unless an extension is granted.

Visit the European Chemicals Agency website for a full list of lead exemptions.

Alternatives to Lead Solder

RoHS works to reduce the risk of lead exposure by limiting the amount of lead used in electronic devices. 

As a result of RoHS legislation, many electronics manufacturers no longer use lead. RoHS pushes industry to innovate substitutions for restricted hazardous materials. Many manufacturers and scientists are researching and using alternatives to lead soldering, including solders containing tin and copper, silver, or other additives.

The most popular lead solder alternative is a solder combining tin, silver and copper known as SAC solder. While SAC solder is now widely used by many in the electronics industry, many changes had to be made in manufacturing processes before the solder could be used. SAC solder has a higher melting point than lead-tin solder, so many products had to be redesigned to withstand higher temperatures.

Another, more experimental alternative to lead solder is the use of ECAs, polymers (materials like silicone) that contain small flakes of conductive metal like silver. These materials stick to circuit boards and the metal works to conduct electricity. The advantage of ECAs is that they can be applied to circuit boards at a much lower temperature than other lead solder alternatives.

Lead-Limiting Legislation

RoHS is the main legislation that limits lead in electronics. However, other legislation has been passed that controls lead in electronic waste (e-waste). 

The United States Environmental Protection Agency (EPA) has several regulations that address the disposal and cleanup of e-waste that contains lead. For example, the EPA has rules for the disposal of cathode ray tubes (CRTs), which contain lead. Visit the EPA website for more information on e-waste regulations.

Table of Contents

• Properties of Cadmium
• Cadmium in Electronics
  • Rechargeable Batteries
  • Semiconductors
  • Plating
• Toxicity of Cadmium
• RoHS: Restriction of Hazardous Substances
  • RoHS Cadmium Exemptions
• RoHS and Cadmium: A Reduction of Risk
• Cadmium-Limiting Legislation

Cadmium is a heavy metal used in the manufacturing of many electronic devices. Cadmium’s use is limited by the European Union’s RoHS directive due to cadmium’s high toxicity.

Properties of Cadmium

Cadmium is a heavy metal used in electronics. Heavy metals are metals with relatively high density that are toxic at low concentrations, meaning a small amount of the metal is toxic.

Cadmium is naturally occurring and can be found in mineral deposits in the earth’s crust. The chemical symbol for cadmium is Cd and the atomic weight (the total weight of the atoms making up an element) is 112.41 g/mol.

Cadmium is often produced as a byproduct of zinc mining. Around 14,000 tonnes of cadmium are produced annually, mainly by top global suppliers Canada, the U.S., Australia, Mexico, Japan, and Peru.

Characteristics that make cadmium popular in electronic manufacturing include its malleability, high conductivity (ability to conduct electricity), and its resistance to corrosion.

Cadmium in Electronics

Cadmium is used in electronics either as pure cadmium, or, more often, as a compound with another element. 

Rechargeable Batteries

About 75% of cadmium used in manufacturing is used to produce cadmium-nickel rechargeable batteries, used in electronics like cell phones. Batteries are not restricted by the RoHS directive.

Semiconductors

Cadmium selenide, a cadmium compound, is an easily shaped metal that is most often used as semiconductors. Semiconductors can conduct electricity in high heat, but not in low heat. Cadmium is a good semiconductor because it is highly resistant to high temperatures. Semiconductors like cadmium selenide have a conductivity (ability to conduct electricity) that lies in between a conductor (like metal) and a non-conductive insulator (like ceramic). As temperature rises, the conductivity of the semiconductor increases, and the cadmium material can act as a conductor. At low temperatures, the same material blocks the flow of electricity. 

Semiconductors are found in most electronic devices today. Semiconductors have an extremely wide variety of functions, but generally they work to amplify signals in a circuit, convert energy, and pass current in a specific direction.

Plating

Cadmium’s resistance to corrosion makes it a popular metal to use as a protective shield against corrosion in electronics and other metals. Cadmium plating, also known as cad plating, offers low levels of electrical resistance, protects against rust, and can be soldered like tin to attach metals.

Toxicity of Cadmium

When products containing cadmium are not disposed of properly, particularly when they are burned, cadmium is released into the air. While the main source of airborne cadmium is the burning of fossil fuels, disposal of electronic waste can also release cadmium. 

Another route of cadmium exposure is through working in a factory that produces electronics or electronic components containing cadmium. Inhalation of cadmium is an occupational hazard.

Long term exposure to cadmium can cause serious harm to human and animal health.

Exposure to cadmium is most famous for causing a degenerative bone disease, Itai-itai disease. This disease was caused by cadmium poisoning contracted as a result of mining. Cadmium is highly water soluble, and so as mining byproducts that contained cadmium were released into a nearby river, cadmium pollution occurred. Eventually, cadmium was absorbed into crops irrigated by the river, causing widespread disease.

Cadmium can also cause lung irritation, kidney disease, and lung cancer. The U.S. Environmental Protection Agency has classified cadmium as a probable human carcinogen.

Cadmium also has negative environmental impacts. For example, in aquatic organisms, long term exposure to cadmium can cause death and harm to growth, reproduction, immune systems, and development.

RoHS: Restriction of Hazardous Substances

RoHS stands for Restriction of Hazardous Substances. The RoHS directive, issued in the European Union, restricts the use of several hazardous materials in electronic and electrical equipment (EEE). All EEE products sold in the EU must comply with RoHS.

RoHS restricts the use of ten hazardous substances in electronics, including cadmium. Electronic devices may only contain these substances in amounts lower than 1000 ppm. The allowable amount for cadmium is 100 ppm.

The materials include:

• Cadmium (Cd)
• Mercury (Hg)
• Lead (Pb)
• Hexavalent Chromium (Cr VI)
• Polybrominated Biphenyls (PBB)
• Polybrominated Diphenyl Ethers (PBDE)
• Bis(2-Ethylhexyl) phthalate (DEHP)
• Benzyl butyl phthalate (BBP)
• Dibutyl phthalate (DBP)
• Diisobutyl phthalate (DIBP)

Any manufacturer, importer, or distributor of electronic and electrical equipment (EEE) sold on the EU market must be compliant with RoHS. 

EEE regulated under RoHS includes a wide variety of electronic products separated into eleven categories, ranging from large household appliances to medical devices. The eleventh category is all-encompassing, as it includes any EEE not covered in the previous ten categories. 

Read more about how to ensure compliance with RoHS: What is ‘RoHS Compliant’?

RoHS Cadmium Exemptions

While alternatives to cadmium in electronics exist and are in the process of being refined, exemptions do exist under RoHS for the use of cadmium in certain applications and electronic categories.

Visit the European Chemicals Agency website for a full list of cadmium exemptions.

RoHS and Cadmium: A Reduction of Risk

RoHS works to reduce the risk of cadmium exposure by limiting the amount of cadmium used in electronic devices. While a product that is RoHS compliant may still contain cadmium, it is present in such small quantities that it poses a lower risk if humans are exposed.

Cadmium is most toxic at high levels of exposure. Lower amounts of cadmium in electronics means there is a smaller chance of high exposure, both for users if a cadmium-containing device breaks, and also for manufacturers of cadmium-containing devices.

While cadmium may still be used in electronics, it is limited to amounts less than 100ppm. Ppm stands for “parts per million.” In other words, in an electronic device, cadmium may only make up .01% or less by weight. This is a fairly small amount of cadmium. 

Because of this limit, some manufacturers no longer use cadmium. Additionally, RoHS pushes industry to innovate substitutions for restricted hazardous materials. Many manufacturers and scientists are researching alternatives to cadmium, such as zinc alloys or gold.

Cadmium-Limiting Legislation

RoHS is the main legislation that limits cadmium in electronics. However, other regulations exist that limit the use of cadmium in consumer products. For example, the United States ASTM Standard F 963-17: Requirements Standard Consumer Safety Specification for Toy Safety requires surface coatings used in toys to contain less than 75ppm cadmium. 

In addition to its RoHS legislation, the state of California passed Proposition 65, which limits the use of cadmium in certain products, including several electronic devices.