Blinded by Science blog 12: Mercury danger from home CFLs.

We’ve made it to the latter half of April and the weather seems to be finally turning.

Probably turning into this.

With the advent of spring and soon summer, the days are continuing to get longer so you’re probably not turning on lights as often as you did during the fall and winter.  So with my wonderful and obviously appropriate timing, today I will answer a question about compact fluorescent light bulbs (CFLs).

Steve P. asks, “I recently broke a CFL lightbulb in my house.  I know that CFLs contain mercury (although I am not sure what part contains the mercury).  How much mercury was I exposed to from the broken lightbulb?  How does this mercury exposure compare to mercury from eating fish?  Am I going to die?”

To answer this question, it’s probably a good idea to first explain what mercury is and why it is dangerous.  Mercury is a metal, though unlike other metals, it is found as a liquid at room temperature.  This property has caused mercury to be known by another name, quicksilver.

 

Nope. Wrong one.

There we go.

There are a lot of dangers associated with mercury and certain mercury compounds.*  Metallic mercury (elemental mercury), which is the type that is liquid at room temperature, does not tend to pass through intact skin and if swallowed, does not get absorbed readily by the gastrointestinal tract.  However, metallic mercury tends to vaporize quickly and it passes through the lungs into the bloodstream if you breathe this mercury vapor in.  On the other hand, organic mercury compounds like methylmercury are readily absorbed into the body through the gastrointestinal tract.  In general, they are not easily absorbed through intact skin, though there is a form, dimethylmercury, which can rapidly enter the body through the skin.

The nervous system is particularly susceptible to mercury, so health concerns related to mercury exposure include: loss of peripheral vision (methylmercury); impairment of speech, hearing or walking (methylmercury); insomnia (elemental mercury); headaches (elemental mercury); skin rashes (inorganic mercury); or memory loss (inorganic mercury) (1, 2).  Damage to the gastrointestinal tract or to the kidneys can also be the result of mercury exposure.

With regards to sources of mercury exposure, due to the nature of food chains and the way mercury is absorbed by fish, mercury can become concentrated in certain types of fish.  The higher on the food chain the fish is found, the more mercury found in the fish.  In fact, here is a handy table that shows the amount of mercury in various species of fish.  It is important to note that the type of mercury found in fish tends to be methylmercury, which is a highly toxic compound of mercury.  Eating small amounts of fish is unlikely to cause problems for the majority of people (though it is important to limit the amount of fish consumed that are relatively high in the food chain).  However, pregnant women are advised to stay away from certain types of fish during pregnancy because the mercury can cause problems for the developing nervous system.

Due to the physical requirements of creating CFLs, mercury vapor is necessary for the CFL to function.  There is only a small amount of mercury in each light bulb, about 4 milligrams on average.  And when these bulbs are broken, only a tiny fraction of the total mercury is released, though the longer you let the broken bulb stay there without cleaning it up, the more mercury is released.  In other words, as long as you clean up the broken bulb quickly (and according to the appropriate procedures!!), the amount of mercury released will not pose a health hazard.

Also, from what I can find, the type of mercury in CFLs is elemental mercury which is not quite as dangerous or toxic as an organic mercury compound such as the methylmercury found in fish.

So in conclusion, mercury is a dangerous compound, though the extent of the danger and the damage caused is based on the type of mercury compound and the route of exposure.  Methylmercury can be found in the tissues of some fish while small amounts of elemental mercury are found in compact fluorescent light bulbs.  A small percentage of what is found in these light bulbs can be released if the light bulb breaks, though it is not enough to cause worry (though be certain to clean up the broken pieces of the bulb properly and dispose of these pieces properly as well).

Overall, you have less to worry about from the mercury exposure from a broken CFL than you do from the mercury exposure from eating fish, and even that exposure should not cause you much worry as long as you don’t eat too much fish.

*Not every compound containing mercury is equally dangerous.  Ethylmercury, which can be found in thiomersal (thimerosal), has different properties from its more dangerous methylmercury cousin.  I would not be surprised if I get a question that requires me to go more in depth on this in the future, but for now, please understand that different chemical compounds have different physical properties (including toxicity), even if they contain some of the same atoms.

Blinded by Science blog 11: What, if anything, does the father contribute to the epigenome?

Posting the last entry, I realized that I’ve had this blog for over a year.  That’s kinda crazy to think about.  Now I’m not one for introspection . . . okay, that’s a ridiculous lie.  I partake of introspection quite a bit, though it is debatable whether I am able to glean any insights into myself from it.  Wait.  Does that count?  You’ll allow it?  Sweet!

Anyway, it is rather remarkable the differences a year can make.  New city.  New state.  New job.  And yet, some things haven’t changed.  I still really enjoy doing this, communicating science to others.  Hopefully, I am able to continue this with the same level of enjoyment.  And as always, for those of you that read the blog and/or contribute questions, thank you!

Now enough sappiness.  On to the question!

Okay, just a little more sap.

Chris H asks, “Epigenetics is quite the buzz-word of late. What, if anything, does the father contribute to the epigenome? Is it a percentage? Or certain things?”

Yay!  Another biology question!  I really enjoy these.

Before I begin, let’s do a little recap.  Remember how I earlier gave a brief explanation of genetics?  Basically, DNA holds a person’s genetic information; the information is converted to RNA and then translated into proteins which do things for the cell, lots of things.  This whole process, from DNA to RNA to protein to beyond, is very tightly controlled and regulated.  In fact, for most genes, the most important form of control is transcriptional control, which deals with the conversion of the information from DNA to RNA.  This makes sense.  Controlling at this step ensures that the cell does not create unnecessary, and therefore wasteful, intermediates.

One of the methods of transcriptional control is at the level of chromatin structure.  Chromatin is the combination of DNA with proteins and other macromolecules.  It not only protects your DNA but also condenses it so that it can fit inside the nucleus of each of your cells.*  But condensing the DNA enough to fit in the nucleus makes it difficult for the proteins that transcribe the RNA from DNA to read the code and do their job.  So the cell has to loosen the chromatin around genes when they need to be “turned on” and transcribed.  In addition, not all cells need every gene product the genome codes for.  Muscle cells don’t need to make proteins necessary for bone cells, and red blood cells would have problems if they produced the adhesion proteins that keep intestinal cells held to each other without leaking.  So body cells need a way to keep some genes “turned off”.  So the cell will add chemical modifications to the chromatin proteins which cause the structure to loosen (allowing for more gene transcription) or cause the structure to tighten (limiting gene transcription).

Another type of transcriptional control occurs when the chemical structure of the DNA itself is modified.  One of the four DNA bases, cytosine, has a methyl group (a carbon atom that is bonded to three hydrogen atoms) added to it to become 5-Methylcytosine.  It still pairs to guanine, but regions that contain high amounts of this modified base are less active when it comes to transcription.

It is important to understand that neither of these types of control change the underlying DNA code, they merely change the behavior of genes, allowing some to be transcribed more while others are transcribed less.

But what do these transcriptional control mechanisms have to do with the question at hand?  Epigenetics is the study of external or environmental factors that turn genes 'on' and 'off' and affect how cells 'read' genes.  And an epigenetic trait is a “stably heritable phenotype resulting from changes in a chromosome without alterations in the DNA sequence”.  So these two transcriptional control mechanisms are examples of epigenetic modifications that occur in a chromosome.

Additionally, due to their nature and purpose, these changes tend to be inherited by the daughter cells after a cell divides.  Amongst other things, this allows a cell to keep certain genes turned off throughout its descendants, which can function as another layer of protection so muscle cells do not produce proteins that are only necessary for bone cells or brain cells produce proteins that are only necessary for liver cells.

But with regards to the question, do these epigenetic markers survive into the next generation?  And the answer is . . . drum roll please . . .

Eh.  Close enough.

Nope.  They do not.  Except when they do.

This is biology we’re talking about.  Exceptions abound.

Normally, after a sperm and an egg meet and fertilization occurs, the epigenetic markers are wiped clean.  Remember that epigenetic markers help silence genes in one cell type that are only used by a different cell type.  So the markers must be removed so that all the different cell types can develop properly (the markers will be replaced as cellular differentiation occurs).  In mammals, it is thought that this process of removal occurs very early in life, just after fertilization.

But some genes keep their epigenetic markers after fertilization.  Imprinted genes are able to keep their epigenetic markers past fertilization (though they are not the only type of genes that can).  Imprinted genes can be inherited from either the father or the mother.  It is currently estimated that about 1% of mammalian genes are imprinted.

As for how much the father contributes to the epigenetic state of the offspring, it is not currently known.  Epigenetics is still a relatively young field of study.  However, it is known that the father does contribute at least some epigenetic markers so it isn’t zero.  My guess (and it is completely a guess since this is not my field of study and I couldn’t find anything about it while researching for this post) is that the father and the mother each contribute roughly the same amount to what little epigenetic markers survive being wiped clean after fertilization.

*It is estimated that each cell in the human body has about 2 meters of DNA in the nucleus.  It is also estimated that there are about 50 trillion cells in the human body.  So there is about 100 trillion meters of DNA in your body, enough (as this source mentions) to make it to the Sun and back more than three hundred time!

Blinded by Science blog 10: Is nuclear energy dangerous?

Whoops!  It has been awhile.  Sorry!  I was partway through this blog post when I got a new job that required me move to a different state.  A new job writing scripts for online science tutorials.  In other words, I got hired to basically do what I started this blog to practice doing: communicating science.  As such, I let the blog fall by the wayside for the past few months.  After having a couple people tell me they liked reading the blog and I should get back to writing it (which is a couple more people than what I thought read the blog), I’ve decided to get back to writing (I hope).

Anyway, for this post, Christian S. asks, “Is nuclear energy dangerous?”

Courtesy Archive.org

Yes.

But then again, lots of things can be dangerous.  Driving cars can be dangerous.  Peanut butter can be dangerous.  Even stairs can be dangerous (especially after leg day).

Or if you are Charles Xavier.

But being dangerous doesn’t mean that something is bad or worthless.  It comes down to, do the benefits outweigh the possible harms?  So with today’s blog entry, I’m going to start off describing what nuclear energy is followed by how nuclear energy is dangerous (actually answering the question asked).  Finally I will talk about the benefits of nuclear energy.

So what is nuclear energy?

As I’m sure we all remember from science class, atoms are the smallest unit of matter that still has properties of an element.  All atoms, no matter which element, are made up of smaller particles called protons, neutrons, and electrons (which are made up of even smaller particles that I’m not going to go into because that’s a confusing rabbit hole I’ll most likely get lost in).  The dense core of the atom, the nucleus, is made up of protons and neutrons and electrons orbit around it.  Each atom of an element has a specific number of protons in its nucleus, so an atom that has 8 protons in the nucleus has completely different properties from an atom that has 9 protons in its nucleus (8 protons is oxygen while 9 protons is fluorine).  It is possible for a nucleus of a specific atom to have a different number of neutrons as another nucleus of the same type of atom.  Atoms that have the same number of protons but different numbers of neutrons are called isotopes.  As the number of protons and neutrons in a nucleus increases (most number of protons in an element discovered so far is 118 in the element Ununoctium), some elements become unstable and can break down.  When this happens, they release protons and neutrons from their nucleus in an effort to become more stable while also releasing energy.  This is known as radioactive decay.

Nuclear power plants use the process of nuclear fission to produce electricity.  In simplistic terms, nuclear power reactors would shoot a neutron into the nucleus of an atom of some fissionable material (such as uranium) which is unable to stably absorb the neutron.  The nucleus then splits into smaller fragments, which also releases energy, radiation, and more neutrons.  These neutrons can hit other uranium atoms causing them to split as well, releasing more energy, radiation, and neutrons which can hit other atoms.  This chain reaction can continue with no further outside involvement until all the fissionable material has been used up.  However, nuclear power reactors control the chain reaction through a variety of processes such as the use of materials that can stably absorb neutrons (the fewer neutrons flying around, the more controlled and slower the reaction progresses).

The energy released during fission heats water to create steam.  The steam is used to spin a turbine that produces electricity.

Dangers:

Before I begin talking about the dangers associated with nuclear energy, I will mention a danger NOT associated with nuclear energy, an explosion like a nuclear bomb.  It is impossible for a nuclear power plant to explode like a nuclear bomb (Truth #2).  Nuclear plants do not use uranium that is enriched enough.

That said, there is always a chance that an accident could occur at a nuclear power plant.  The worst type of accident is a meltdown, where the core of the reactor gets too hot and the fuel cracks, releasing radioactive gas; or the hot, radioactive material melts and damages the protective structures so it can reach the environment.

In the event of a nuclear power plant accident, danger exists from the plume of radioactive material that may be released and contaminate people and things that are outdoors, from radioactive material that is ingested or breathed in, or from radiation exposure to those living nearby the power plant.  Radiation can damage the DNA in the cells of the body, either causing mutations or the death of the cells.  If a high enough dose of radiation is received all at once, death occurs due to cellular death and organ damage.  Lower levels of radiation exposure can cause genetic mutations that could lead to cancer, even years later.  Even a relatively minor incident in which radioactive material leaks into the environment could cause health problems or environmental damage.*

The chances of an accident occurring are very small, however.  Reactors are designed with multiple layers of protection and redundancies to make the chance of an incident occurring very small.  In fact, a type of incident like the one that occurred in Chernobyl could not occur here in the United States because that type of reactor was never built here (Truth #7).

And just as a nice visual aid to illustrate the difficulty of the public being exposed to high levels of radiation (plus I love the source), here’s how safe you would be swimming in the pool used to store spent nuclear fuel rods until they were safe for transport.  Really makes you think, though that whole lead poisoning thing at the end means you shouldn’t try it.

*It all depends on the dose of radiation you receive and how often you receive it.  Humans are exposed to numerous sources of radiation in their everyday lives (1, 2).  In fact, you absorb slightly more radiation from eating a single banana than you do from living within 50 miles of a nuclear power plant for one year.  Our body is usually able to repair the damage caused by this low level of radiation.

Benefits:

One of the major benefits of nuclear energy is a lack of air pollution production or carbon dioxide release.  You could easily make the argument that the type of pollution that would occur if a nuclear incident occurred is more damaging to the environment and human health than the air pollution and carbon dioxide release of traditional power plants, but it comes down to the difference between a potential harm vs a guaranteed and currently occurring harm.

Also, the “energy density” of uranium (and other nuclear energy material) is greater than that of coal, oil or natural gas.  In other words, if you have a pound of uranium vs a pound of coal, the energy that you could harvest from the uranium is many times greater than what you could harvest from the coal.  Nuclear power could thus reduce our dependence on fossil fuels, and specifically reduce our dependence on foreign oil.  Additionally, the cost of producing energy via nuclear power is lower than the cost of producing energy with fossil fuels.

And just as an aside, it is interesting to note that in the 50+ years of commercial nuclear power, there has been no radiation-related health events in the public linked to the operation of nuclear power plants.

So Christian, to answer your question, there are dangers involved with nuclear energy, but those dangers are taken into account in the design of reactors and the risk of something bad happening is very small.