11/10/2015: Recently I had a hair test done on myself. I had already done my wife's hair test, but now it was my turn.. I had several things that I wanted to check out that really only hair testing can do (unless you have a boatload of cash to spend with a toxicologist). The first of the things that I wanted to check out was whether or not I was possibly ingesting too much arsenic from a rice protein powder that I had been taking for several years.
The reason that I was concerned is that it is impossible to know if my protein powder had been properly monitored or if the rice used in production was purchased from the United States. Rice from the United States has been shown to often have high levels of arsenic and numerous articles and exposes have been done on the topic. This occurs because crops and fields have been contaminated with pesticides that are arsenic-based. This is very unfortunate, of course, as brown rice is a staple of some of the healthiest peoples in the world. Brown rice also increases nitric oxide - need I say more?
For those who may be wondering why I would consume rice protein of all things, considering that it does not excel in bioavailability or other standard protein quality measures. My reasoning is the following:
a) Rice protein powder is one of the few proteins out there that a man can purchase undenatured, i.e. CFM or cross flow microfiltered such that the protein is not overheated. If you overheat any protein, it will release significant amounts of free glutamine, which is, effectively, "MSG." I have written quite a bit about this on my web site, but here is one example: Whey, Excitoxins and Free Glutamine. (NOTE: All wheys have glutamic acid listed on the label. What varies, depending on the heating, is how much free glutamine is released. Free glutamine is NOT listed on the label.)
b) Vegan proteins are generally less stimulatory of IGF-1, which is very important from the anti-aging standpoint. Young guys don't worry about this, but I'm in my mid 50's and have a little different perspective. And, yes, I know IGF-1 is good for building mass. However, IGF-1 revs up mitochondria and increases free radical production. See my page on How to Lower IGF-1 for some basic information on the subject.
Even if you disagree with the above, you can see that I am trying to protect my health and should not have to worry about a buildup of arsenic in my tissues! Again, this is primary reason I had a hair test done: it is an inexpensive way to find out if arsenic and other heavy metals have been possibly building up in my tissues. The hair test cost me a little over $100, and I did it through Direct Labs and Direct Labs uses Doctor's Data. (I have no affiliation.) Here are my results:
I have more to say about these results but will cover that in some other pages. As you can see, my arsenic is on the high side. I am at about the 70th percentile, and it is one of my highest scores. Now I certainly cannot prove that it was the rice protein. Arsenic can be in water for example. But I think it is very likely it was the rice protein and will test it by quitting the rice protein and then testing again after a few months. If my arsenic score goes down, then the evidence is even stronger that the rice was probably the culprit.
The report that comes with Doctor's Data is packed with interesting information and here is an example:
"In general, hair provides a rough estmate of exposure to Arsenic (As) absorbed from food and water. However, hair can be contaminated externally with As from air, water, dust, shampoos and soap...As can cause malaise, muscle weakness, vomiting diarrhea, dermatitis, and skin cancer. Long term exposure may affect the peripheral nervous, cardiovascular and heatopoietic systems. As is a major biological antagonist to selenium." 
The latter is particularly concerning to me as I am a flexitarian, i.e. I consume a largely plant-based diet but eat a little bit of animal-based protein. I have calculated my selenium and it came out on the low side. The last thing I need, apparently, is arsenic! (I have started taking supplemental selenium recently.)
I know some guys out there feel like you cannot worry about everything and a few toxins can't hurt you if you just "live healthy." I have to respectfully disagree with point. Heavy metals are "kryptonite" and can take down the best of us. Let me give you just a couple of sobering examples:
1. Cancer. A lot of research has shown arsenic as a potent carcinogen. Those of you who have been digging into some of the recent genetic research will understand the gravity of the mechanism by which arsenic can accelerate cancer:
"Exposure to arsenic, an established human carcinogen, through consumption of highly contaminated drinking water is a worldwide public health concern. Several mechanisms by which arsenical compounds induce tumorigenesis have been proposed, including oxidative stress, genotoxic damage, and chromosomal abnormalities. Recent studies have suggested that epigenetic mechanisms may also mediate toxicity and carcinogenicity resulting from arsenic exposure." 
2. Neurotoxicity. Researchers have noted the pesticides and environmental factors seem to play a role in Parkinson's disease and the destruction of dopaminergic neurons in the brain. Recent research shows that arsenic and dopamine can synergistically acclerate this type of neurotoxicity and, therefore, arsenic-based pesticides may be one of the root causes of Parkinson's. 
CONCLUSION: Hair testing can provide valuable information on potential toxins in your system including arsenic. I agree that a couple of months of elevated arsenic exposure may not make that much of a difference. But consuming excess arsenic in concentrated protein powders for decades could end up unraveling all the hard work you have to put into improving your health.
1) Journal of Toxicology, Volume 2011 (2011), "Arsenic Exposure and the Induction of Human Cancers"
2) Environ Health Perspect 119:11-19 (2011), "An Emerging Role for Epigenetic Dysregulation in Arsenic Toxicity and Carcinogenesis"
3) TOXICOLOGICAL SCIENCES, 2007, 102(2):254 261, "Synergistic Neurotoxic Effects of Arsenic and Dopamine in Human Dopaminergic Neuroblastoma SH-SY5Y Cells"