Samhain wrote:

As a scientific researcher, can you correct me on the following impression I've been given by bad science reporting? "On the topic of cancer, it seems that as one ages the probability of acquiring cancer approaches 1. While the risks can be reduced by a healthy diet, not smoking, not going outdoors in daylight, not using cellphones, not breathing air in cities or highly populated countries, and so on, it's sadly a fact of life right now. The list of things that cannot cause cancer is probably smaller than the list of things which can." I'm probably wrong about this. I hope.


Different things in the environment cause cancer through their ability to perturb DNA and cause mutations. Although there are many mutagens, some are worse than others. People often develop cancer as they age from a combination of an increased probability of encountering mutagenic elements in the environment and because of the aging process itself, which may decrease the availability of proteins that are necessary for repairing DNA damage and through an increase in toxic endogenous chemical reactions, like free radical production. If a mutation arises in a gene that is involved in cell growth and division, this can lead to cancer. Here are different types of DNA damage that may lead to cancer (both endogenous and exogenous):


Types of damage
There are five main types of damage to DNA due to endogenous cellular processes:
1. oxidation of bases [e.g. 8-oxo-7,8-dihydroguanine (8-oxoG)] and generation of DNA strand interruptions from reactive oxygen species,
2. alkylation of bases (usually methylation), such as formation of 7-methylguanine, 1-methyladenine, 6-O-Methylguanine
3. hydrolysis of bases, such as deamination, depurination, and depyrimidination.
4. "bulky adduct formation" (i.e., benzo[a]pyrene diol epoxide-dG adduct)
5. mismatch of bases, due to errors in DNA replication, in which the wrong DNA base is stitched into place in a newly forming DNA strand, or a DNA base is skipped over or mistakenly inserted.

Damage caused by exogenous agents comes in many forms. Some examples are:
1. UV-B light causes crosslinking between adjacent cytosine and thymine bases creating pyrimidine dimers. This is called direct DNA damage.
2. UV-A light creates mostly free radicals. The damage caused by free radicals is called indirect DNA damage.
3. Ionizing radiation such as that created by radioactive decay or in cosmic rays causes breaks in DNA strands. Low-level ionizing radiation may induce irreparable DNA damage (leading to replicational and transcriptional errors needed for neoplasia or may trigger viral interactions) leading to pre-mature aging and cancer.
4. Thermal disruption at elevated temperature increases the rate of depurination (loss of purine bases from the DNA backbone) and single-strand breaks. For example, hydrolytic depurination is seen in the thermophilic bacteria, which grow in hot springs at 40-80 °C.The rate of depurination (300 purine residues per genome per generation) is too high in these species to be repaired by normal repair machinery, hence a possibility of an adaptive response cannot be ruled out.
5. Industrial chemicals such as vinyl chloride and hydrogen peroxide, and environmental chemicals such as polycyclic hydrocarbons found in smoke, soot and tar create a huge diversity of DNA adducts- ethenobases, oxidized bases, alkylated phosphotriesters and Crosslinking of DNA just to name a few.
UV damage, alkylation/methylation, X-ray damage and oxidative damage are examples of induced damage. Spontaneous damage can include the loss of a base, deamination, sugar ring puckering and tautomeric shift.


The point is that we should minimize exposure to cancer causing agents as much as possible. Some ways to do this, like not smoking and not living next to nuclear power plants, are easier than others. Although there are many things that cause cancer, we know HOW they cause cancer and what we can do to decrease exposure.

Of course. What do you have in mind, though? Biofuel causes similar rates of pollutants, solar energy, hydroelectric, geothermal (which has its own environmental problems), and wind power aren't going to come close either. I guess the only solution at this point is to reduce energy consumption in general?


I am at a university where there are several labs that are focused on this very question. They seem to believe that technology can be discovered to solve these problem. We just need the political power to actually invest in these technologies. Moreover, solar power CAN work, it is just expensive and we need to figure out better ways to store and transport the electricity. We do, however, have enough land to do this. Here is the website of Professor Nate Lewis, who is working on this. You can watch some interesting talks on this topic. I recommend the Feb 2008 JPL talk, where he shows that if we want to use nuclear power to solve our energy needs, we would need to build 10,000 new nuclear power plants!!! This would mean one new plant every other day for the next 50 years! Not feasible (or a good idea!)

Anna