Settling the Mercury Emission Debate

Mercury is a known neurotoxin. It hampers neurological development, impacts the cardiovascular system of adults and wild animals dependent on fish.

  • In a 2003 study 1 in 12 American women (8%) of child bearing age had blood mercury levels beyond levels considered safe by EPA (Center for disease control and prevention).
  • More than 300,000 newborns are exposed to the risk of mercury poisoning every year.
  • Methyl mercury is the most dangerous form of mercury and exposure to this chemical is primarily through the consumption of fish and shell fish.
  • 40% of US mercury emissions come from coal fired power plants.

Coal based power and Mercury

A single coal fired power plant releases 45 to 50 tons of mercury each year. With existing technology, it is possible to reduce mercury emissions per power plant to 15 tons per annum. Power plants vary widely in their per KWH mercury emissions. Thus one plant releases 0.2071 pounds of mercury per GWH (giga watt hour) of electricity produced while another produces only 0.0607 pounds per GWH (giga watt hour). This works out to 0.093 to 0.027 milligrams of mercury emitted for per KWH of electricity produced.

Environmental Cost of Bulbs and CFLs

A Compact Fluorescent Lamp contains 4-5 mg of mercury. Advocates of CFL technology say that the amount is miniscule and should not deter home owners from investing in CFL lights. The mercury debate is not as simple as it seems. A billion CFL’s are disposed off every year. This is when most homeowners in United States and Canada are yet to shift to CFL lights. Should the whole world shift to CFLs the number of CFLs disposed would grow manifold. Whenever you hear the argument “less mercury – only 5 milligrams per CFL” remember that it is not just 5 milligrams but - one billion times 5 milligrams that we are actually talking about.

It is all a matter of availability of options. Bulbs polluted less than kerosene lanterns and were welcome. CFLs caused even less pollution. As long as a better technology was not available the argument of CFLs reducing mercury pollution, held some water – incandescent bulbs are worse mercury polluters. Once LED lights became a practical proposition CFLs became outdated. Compared to heavy metal free eco friendly LED lights, CFLs are practically a smokestack!

Let's do the Math

There are a many conflicting claims about the number of bulbs and pollution. Many proponents just throw numbers at the audience. Let us do the Math ourselves to understand the truth behind the environmental impact of lighting.

Number of bulbs in the United States

There are close to 100 million (Approximately 103 million) households in United States and an average house hold has 45 light bulbs. This makes for a total of 4.5 billion (100 million X 45) light bulbs in residential properties alone.  The average wattage of a bulb in a US household is 50 watts. This makes for a total lighting wattage of 225 million KWH in United States.

A traditional incandescent lamp lasts 1000 hours. Assuming a daily usage of 8 hours the life of incandescent bulbs, CFLs and LED lights will be

(Please note: We have made some assumptions that may not apply to a household. For example, it may not be realistic to assume all bulbs in a household are on for 8 hours a day. To accurately calculate these averages for a US household would be a rather monumental equation that would overwhelm the purpose of this discussion.)

  • Incandescent bulbs – 8 months
  • CFL's – 25 months (2 years)
  • LED's – 125 months (more than 10 years).


Since CFLs need replacement every 2 years it can be assumed that at least half the CFLs or 2.25 billion CFLs (we are assuming that all lighting devices are CFL based) in the United States will need replacement every year.

Potential mercury emissions due to CFLs

Can we now estimate the amount of mercury that will be released in the environment every year – 2.25 billion X 5 milligrams = 11.25 billion milligrams or 11,250 kilograms of mercury every year! Only 5 milligrams of mercury (equal to that contained in a single CFL) is enough to pollute more than 150,000 liters of water. The amount of mercury from the disposal of 2.25 billion CFLs would be enough to pollute 2.25 billion X 150,000 liters of water!

Admittedly the amount of mercury released will be lower as a few CFLs will be responsibly recycled.  Yet it will be enough to poison every liter of water over time. Already at least half the water bodies of United States suffer from mercury contamination.

Add to it the fact that CFLs emit UV light that may damage precious art objects and they no longer remain the knight in shining armor out to save the earth from green house gas emissions.

Potential mercury emissions due to Incandescent Bulbs

CFLs are bad at mercury emissions but incandescent bulbs are worse. Bulbs contain no mercury but they waste a lot of electricity. Electricity in turn is produced by burning coal and coal contains mercury. The mercury in a CFL that is disposed irresponsibly will leach into the soil and from there into food and water. The emissions from power plants on the other hand are of mercury vapors that are potentially more toxic.

In some states coal fired power plant produces 0.0234 milligrams of mercury (besides carbon-di-oxide and oxides of sulfur and nitrogen) for producing 1 KWh of electricity. 2008 data of mercury emissions (EPA’s Toxic release Inventory) demonstrate that emissions of mercury for the 50 most polluting mercury power plants range between 0.027 to 0.093 milligrams per KWH. Nevertheless the EPA and citizen action groups are trying hard to decrease the amount of mercury emitted by power plants. Therefore we have assumed the mercury emissions to be in the range of 0.0234 milligrams per KWH.

  Incandescent bulb CFL LED
Mercury contained in bulb (milligrams) 0 5 0
Mercury released in the environment due to electricity
consumption over 6000 hours (milligrams)
9.126 2.5272 1.2636
Total (milligrams) 9.126 7.5272 1.2636


It seems that when it comes to mercury pollution, the bulb is the worst offender. But there is an error in the above calculation. Many experts use this data to demonstrate that CFLs are better. But only 50% of the electricity is produced by coal and at least 25 % CFLs are disposed safely. The calculations need to be modified to reflect this data.

Once we factor in this information it seems that CFLs can release more mercury in the environment than incandescent bulbs. Higher recycling of CFLs is essential to reduce their potential for mercury pollution.

If 35% of the CFLs are recycled, the mercury emission of CFLs and incandescent bulbs would be equal. For any higher recycling percentages than this CFLs will beat incandescent bulbs.  Conversely, if the contribution of coal to power generation decreases or if coal burning plants successfully reduce mercury emissions - CFLs will lose to incandescent bulbs on the mercury pollution front. For people getting their energy from wind, solar or hydroelectricity this is a realistic scenario

  Incandescent bulb CFL LED
Mercury contained in bulb (milligrams) 0 3.75 (5 X 0.75) 0
Milligrams of mercury released in the environment
due to electricity consumption over 6000 hours (50% coal)
4.563 1.2636 0.6318
Total (milligrams) 4.563 5.0136



When that happens, improperly disposed CFLs will become a more dangerous source of mercury emissions than incandescent bulbs.

The Solution - LED Systems

LED lighting systems are probably the most refined lighting system in production today. The demand of LED's for flat panel displays and lighting devices is exploding. Despite huge investments and a quantitative jump in production, manufacturers may not be able to keep pace with the rising demand.

They do not employ any mercury in their constructions. They also emit less greenhouse gases that either bulbs or CFLs due to a number of reasons.  

  • The mercury released by CFLs is 5.01 milligrams and that by bulbs stands at 4.56 milligrams over 6000 hours of operations. LED bulbs produce a minuscule 0.6318 milligrams of mercury in this time frame. This is 7 times less than either CFLs or bulbs.
  • They use around a seventh of the electricity used by bulbs and half that of CFLs.
  • There are no greenhouse gas emissions of reverse logistics as will happen in the case of CFLs.
  • They last for almost a decade compared to a year or less for bulbs and 2 years for CFLs– the greenhouse gas emissions associated with the transport of LED's is obviously less than that for wither lighting device.


Besides greenhouse gases, LED lighting products comprehensively beat both bulbs and CFLs on the mercury pollution front.

Some estimates suggest that lifetime energy savings from a 24 watt CFLs can power a Prius from coast to coast. If it were an LED light (that last 5 times longer and use half the energy of a CFL) the lifetime energy savings would be enough for 10 such rides! Similarly estimates suggest that replacing one incandescent bulb with a CFL in each American home could offset emissions due to 800,000 cars or light 3 million homes – LED's by contrast could offset 1,600,000 cars or light 6 million homes or do both together – light 3 million homes and offset 800,000 cars. Any way you look at it, they trump both incandescent bulbs and CFLs.

Energy Savings Calculator

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