Are solar panels toxic?

As you probably know, solar panels turn sunlight into clean electricity: they’re totally silent, and don’t release any pollution.

Even though solar electricity is clean, you might wonder about the solar panels themselves. What exactly is under that sheet of glass? If you’re a homeowner who is thinking about putting solar panels on your roof, are you putting the health of your family at risk by installing dangerous or toxic materials on your home?

Crystalline silicon (c-Si) solar panels - the type in most common use - are made with non-toxic silicon. There are potentially toxic materials in these solar panels to be concerned about - particularly lead and hexavalent chromium - but the quantities are small enough as to not pose a health concern to a homeowner. Be aware that while there are laws that limit these toxins in some electronics, solar panels are currently excluded. If you want to extra careful about the safety of your panel, look for one that voluntarily meets RoHS standards.

Restriction of Hazardous Substances: EU and California laws

In 2006, the European Union implemented the Restriction of Hazardous Substances Directive 2002/95/EC, often referred to as the EU RoHS for short. It places limits on the the following substances in some electronic equipment:

• Lead (Pb)
• Mercury (Hg)
• Cadmium (Cd)
• Hexavalent chromium (Cr6+)
• Polybrominated biphenyls (PBB)
• Polybrominated diphenyl ether (PBDE)
• Bis(2-ethylhexyl) phthalate (DEHP)
• Butyl benzyl phthalate (BBP)
• Dibutyl phthalate (DBP)
• Diisobutyl phthalate (DIBP)

The maximum permitted concentration for these substances is 0.1% by weight, with the exception of cadmium which has a limit of 0.01% by weight.

California RoHS

The state of California has enacted its own RoHS law, and it’s modelled closely on the European law. The main difference is that two flame retardants are excluded from the California version: polybrominated biphenyls (PBBs) and polybrominated diphenyl ethers (PBDEs). This isn’t surprising, as California has long had laws that require certain products to pass a flammability test.

Which of these toxic substances might be present in silicon solar panels?

Of the toxic materials governed by the EU RoHS and California RoHS laws, there are two that are relevant to c-Si solar panels: lead and hexavalent chromium.

Lead is a heavy metal that is poisonous in large concentrations, and has neurological effects on humans in smaller amounts. Lead contamination can be a big environmental issue: the contamination of the Flint, Michigan water supply is one recent example.

Hexavalent chromium (Cr6+) may be used in chrome plating, paints, pigments, and other coatings. It’s a well-known carcinogen: the environmental activist Erin Brockovich fought PG&E over their dumping of Cr6+ that contaminated groundwater in the town of Hinkley, California. (This story was eventually made into a movie with Julia Roberts in the role of Brockovich.)

Both these materials might be present in your rooftop solar panel. A small amount of lead may be present in the solder that is used to join wires in the panel together. Hexavalent chromium was used as a coating in earlier generation solar panels, but it’s possible that some manufacturers still use it today. In any case, neither lead or Cr6+ will be present in a large enough amount to pose a health hazard to your home.

Verifying that your solar panel meets RoHS standards

Currently, photovoltaic panels are exempted from the RoHS standards in the EU and California. Perhaps the biggest challenge for solar panel manufacturers is to use lead-free solder, which is available but can be difficult to make as durable as solder that does contain lead. Still, there are some manufacturers that have voluntarily met these standards, such as Panasonic and SunPower.

To find out, you will need to examine the product sheet for a solar panels and look for a 2002/95/EC or RoHS specification. For example, the Panasonic HIT+ series has the following note on its product datasheet:

Thin-film solar panels and toxicity

Even though the most common type of solar panel should be considered safe, there is a type of solar cell that can contain higher amounts of toxic materials: thin-film solar cells.

Conventional solar cells are made by cutting wafers from a block of silicon. Thin-film cells, in contrast, may be made from a variety of other elements, including cadmium and selenium.

Cadmium telluride

Cadmium telluride (CdTe) is the most common type of thin-film solar cell in production.

First Solar, a US-based manufacturer, makes attractive PV modules that can be used in home applications. Normally, thin-film cells have quite a bit lower efficiency than c-Si cells, but the latest products from First Solar have up to 18% efficiency, which rivals monocrystalline silicon cells.

First Solar also claims that their product is more environmentally friendly than c-Si cells because of the lower energy inputs required in manufacturing.

However, cadmium telluride has toxicity concerns. It’s harmful if swallowed, and is very toxic to aquatic life.

Copper indium gallium selenide (CIGS)

CIGS is another mainstream thin-film technology. The company Solyndra, now bankrupt, was one of the few companies that attempted to bring CIGS cells into mainstream use. Solar Frontier, a Japanese company, is a current producer of CIGS solar cells. MiaSolé, a company based in California but owned by a Chinese parent, also manufactures CIGS cells.

None of elements used in this type of cell are heavy metals. However, individual elements used in CIGS, such as indium, do have known toxicities.

But that doesn’t mean that the CIGS molecule has the same health risks. However, there is currently no published toxicity or health data for copper gallium indium selenide.

Portable solar panels and thin-film

One of the product categories that you might expect to find widespread use of thin-film cells is for portable power charging devices, but even this is still dominated by c-Si. This is because it’s possible to make crystalline silicon semi-flexible by reducing its thickness.

This type of semi-flexible solar cell is extremely popular for mobile applications such as camping and motorhomes, and small charging devices for smartphones and laptops.

Most flexible and portable solar panels that you’ll find on the market are made of flexible c-Si cells, and not thin-film.

Thin-film solar cells: a health concern?

The most toxic of the thin-film technologies is CdTe, which contains cadmium. It’s also the one in most widespread use. If you’re thinking of going with a CdTe panel, such as those available from First Solar, should you be concerned?

According to a study by Virginia Tech, no. According to the study:

The CdTe compound is less leachable and less toxic than elemental Cd. The risks to the environment arising from broken solar panels during adverse events are considered by reviewing experimental results, theoretical worst-case modeling, and observational data from historical events. In each case considered, the potential negative health and safety impacts of utility-scale photovoltaic installations are low. The need for end-of-life management of solar panels is highlighted in the context of recycling to recover valuable and environmentally sensitive materials. Based upon the potential environmental health and safety impacts of CdTe photovoltaic installations across their life cycle, it is concluded they pose little to no risk under normal operating conditions and foreseeable accidents such as fire, breakage, and extreme weather events like tornadoes and hurricanes.

In other words, cadmium telluride is less of a hazard than metallic cadmium, and even in exceptional cases like a fire, the risks are relatively low.

This doesn’t mean that there is zero risk, which is why the authors highlight the need for recycling at the end of the product’s life.

Cadmium in your home now

Do you have a battery-powered tool, like a drill or dustbuster? There’s a good chance that it has a nickel-cadmium battery. But there’s little risk to you, because it’s safely packaged inside a durable housing. When the product has reached the end of its life, you can take the battery to a Home Depot or Lowe’s and recycle it.

With proper lifecycle handling, there’s no reason that CdTe solar panels can’t be considered just as safe as these other common consumer products.

Bottom line: choose RoHS solar panels if you’re concerned, but solar energy makes the environment cleaner

To be clear, while the health risks from solar panels are extremely low, that isn’t to say that there are zero toxicity concerns, even with panels made with c-Si. In addition, at the end of their life, solar panels will add to our e-waste problem, which is a legitimate environmental and health concern. Fortunately, solar panel recycling is an industry that is growing and will become significant over the next decade or two.

If you want to be extra careful about health and safety issues, look for solar panels that voluntarily meets RoHS standards.

Bottom line: despite the real e-waste problem, solar panels actually help reduce the amount of toxic materials in our environment, such as mercury.

Mercury is one of the most common heavy metal pollutants - it’s the reason why pregnant women are advised to limit their intake. The reason for that mercury pollution? 42% of it is from coal-fired power plants. This means that by choosing solar energy, you’re actually helping to reduce heavy metal pollution in the environment.

If you want to learn more about the environmental benefits of solar panels, including conventional c-Si cells, read our article on the topic.