Category Archives: Guest Posts

From the Rancher’s Mouth: Beef Cattle and the Environment

Confession: my husband, kids and I hardly ever eat beef. In fact, I can’t even remember the last time I bought beef at the store. Not that I don’t like beef – I occasionally enjoy a good hamburger at a restaurant and when we visit my parents I often request steak because my dad cooks a good steak.  Part of the reason we don’t eat much beef is because we only eat meat about 50 percent of the time. My husband used to be a vegetarian because he believes with our growing population it’s more efficient to eat a plant-based diet instead of using resources to raise animals for us to eat. Since having kids, he’s relaxed his approach because getting protein into kids is hard enough without the added difficulty of doing it without meat. As a compromise, when I plan the weekly menu, half of it is vegetarian. When we do eat meat, we don’t usually choose beef because cows are fairly resource-intense to raise (and, frankly, it’s often more expensive than chicken.)

At least, that’s what we think. In complete fairness, I’ve not spent a lot of time looking at the data, so when a cattle rancher with a degree in Environmental Studies agreed to share her perspective on the environmental impact of raising beef cattle, I was really excited. The below guest post by Cassidy  is a bit of an introduction into the environmental conversation around raising beef. Admittedly, this is one perspective on the conversation, and I plan to come back to this issue again in the future. But it’s an important perspective from a very intelligent, well-researched source, and I learned a lot about cattle ranching that I never knew. I hope you learn something new, too. (All pictures courtesy of Cassidy.)

Cassidy lives and works with her husband and six-month-old son on a cattle ranch in east central Colorado, where they raise registered Angus, Red Angus, Hereford and Charolais cattle. She has a B.A. in Environmental Studies from the University of Colorado at Boulder. When they’re not messing with cows, horses or dogs or playing with their roly-poly kiddo, she likes to cook, read, do DIY projects, and cover as many surfaces as possible in plaid and/or glitter. 

–By Cassidy —

I’ve started and almost finished this post many times, but haven’t ever been happy with the result. I struggled with how to format it in a way that wasn’t too wordy while also being direct and informative and as unbiased as possible. The best I could come up with is a broad FAQ of sorts, because I get asked the same questions over and over. This is a very brief overview of a very complicated topic.

Just a disclaimer, I am going to be talking about beef ranching only. I’m also not going to be discussing feedlots—that’s a separate (though very much related) issue.

As a cattle rancher, how do you feel about the argument that people need to eat less beef?
I think people need to eat less (and waste less!) period, beef included. A quarter-pounder contains more than enough calories for a meal; do you really need to supersize it and add more of everything? And how much of that 16-oz steak are you going to eat, and how much are you going to throw away? This country as a whole struggles with consumerism and health, so cutting back across the board—not just in beef—seems to be a good idea to me.

But beef is the least feed-efficient animal, and they take up so many resources!

Flour the baby calf.

Flour the baby calf.

Again, true. Of the four main meat animals (fish, chicken, pigs, cattle), beef is the least feed-efficient animal; that is, it takes more pounds of feed to make one pound of meat (Johnston 2012). Cattle are larger than fish, chicken and pigs and thus take up more room and require more input just to maintain themselves. However, 85 percent of the land where cattle are raised is unsuitable for farming (Explore Beef 2009), so cows are a way to make that land work for us from a food production perspective, while maintaining natural beauty and wide-open spaces.

Another cool thing about wide-open spaces, besides the natural environment for wildlife and just seeing nature do its thing? Carbon sequestration! Grasslands, like forests, are carbon sinks, and some research shows that grasslands produce more in an environment higher in carbon dioxide (North Carolina State University 2001). Grasses require disturbance—grazing—to remain healthy, so well-managed grazing actually helps the environment; I talk more about this in the next section.

Isn’t livestock ranching bad for the environment? Ranchers only care about the bottom line, not the land.
Livestock ranching as it relates to climate change and land use is a big deal. A study by the FAO shows the impact livestock have on the environmental health of our planet (FAO 2006). As a rancher who holds a degree in Environmental Studies from CU Boulder, I get it, I really do. But no, well-managed ranching is not bad for the environment (Alberta Sustainable Resource Development 2008, Explore Beef 2009). The key here is the management, and the American ranching industry has made huge leaps and bounds in the past several decades as far as management is concerned. On government lands, for instance, land health is monitored closely. In years of environmental duress or when the rangeland in question is not up to standard, the number of animals allowed on the permit may be decreased, or a rest period may be implemented (Wiles 2014).

However, it’s hard to get a real read on the nation’s rangeland health as a whole. This article explains it much better than I can.

Ranching and the environment are very closely related—they have to be! Yes, ranchers care about the bottom line. They have to; a ranch is a business. But, ranchers are also stewards of the land, and the health of the environment is often the same as the health of the bottom line. How? Well, ranchers make a large portion of their income (if not all their income) selling cattle. Good grass makes for healthy cattle that produce better milk and raise bigger calves. Since cattle that will be eaten (feeder cattle) are bought and sold by the pound, this is important. Good grass also makes for big, strong, healthy bulls and replacement heifers (yearling heifers chosen to stay in the herd to replace old or culled cattle), which will increase their value to a prospective buyer. Poor grazing management is economically counterproductive, since bad management means less or poorer quality grass which translates to less weight gained or value added.

The environment, of course, includes the water, too. The area where land and a river or stream meets is called a riparian area. Managing this area is, in my opinion, one of the weaker links, but it’s also one of the areas where improvements are being pushed the hardest. Riparian areas are hard to manage, because they’re where cows like to be. It’s cool, there’s water, and the grass is tasty, so it’s not easy to convince the girls that they don’t need to hang out by the creek all the time.

Fenced off pond.

Fenced off pond.

We manage this by giving cows other water sources, and use windmill- and solar-powered water pumps to pump water into tanks fitted with overflow floats or ground tanks so they don’t overflow and get muddy. We also fence off particularly sensitive or boggy areas—sometimes just as much for the cows’ benefit, because cows can get bogged down and stuck and will die if you don’t get to them in time, and it can be pretty dangerous and exhausting work to pull a stuck cow out of a bog. We also use salt and mineral strategically to lure cows away from creeks to water tanks that are easier to manage. When all else fails, the cowboys will ride the creek every day, and push the cows away.

If ranching were all about the bottom line, no one would do it. It’s not a job; it’s truly a lifestyle that you have to enjoy to keep at it. The hours are long and the work is hard, and it’s definitely not as romantic as it seems. My husband and I have never held hands riding off into the sunset on our horses, but we have held (gloved) hands in the pickup checking calves all night long during a blizzard.

I’ve read that cows produce a lot of methane, which is a major greenhouse gas.
Also true! Cows are ruminants and enteric fermentation (methane production) is a natural by-product of their digestive processes, enteric fermentation from beef cattle accounts for about 19 percent of annual US methane emissions (United States Environmental Protection Agency, Center for Climate and Energy Solutions 2009). That’s a big number, but it bears mentioning that while methane is the more potent greenhouse gas, it only accounts for ten percent of all greenhouse gas emissions. The beef industry is working on making animals more efficient in how they process feed—more moderate-framed, high feed-efficiency cattle that don’t require as much input. Our primary goal in choosing herd sires and replacement heifers for our ranch is frame size and efficiency. Our ranch is part of a larger group of ranches, and we provide the bulls to all the other ranches. Choosing moderate-framed bulls with high feed efficiency makes a big impact across all of the ranches, since there are over 16,000 cows. This means that there are 16,000 cows annually that are going to produce a more moderate-framed calf, thus producing less methane and using fewer resources. It also means that we are choosing replacement heifers from a more moderately-sized group of calves. The end goal is to have a very moderately-sized, highly efficient herd that is effective from both an economic and environmental standpoint: smaller, more efficient cattle use fewer resources and produce less methane.

Summer grass meadow.

Summer grass meadow.

One thing to mention here though is that I often hear that grass-fed beef is the better option both health-wise and environmentally. Keep in mind that cattle that are finished on grass rather than grain not only produce more methane because grass is harder to digest (Jones 2014), but because grass-finished cattle live anywhere from 6-16 months longer (Brady 2014) because it takes them longer to reach slaughter weight. This means that they consume more grass, water and space, too.

Isn’t it unfair that one person can own so much land and not allow it to be available for public use?
The ranch that my husband and I work for is about 50 miles away from a large city, with lots of smaller towns in between, and the owner buys up land as it comes up for sale so that it doesn’t get sold to developers. This means that the ranch is not even close to being contiguous, but I think it’s pretty neat because he’s working so hard to make sure that there’s some open spaces left for our children to see.

I know that there are people who have negative opinions about private land ownership, because that land isn’t open to the public for use. While I understand that argument, I think that the end result is more important, and if private citizens have to buy land to save it from being turned into 40-acre lots for homes and subdivisions, then so be it.

What’s more environmentally friendly: 80,000 acres of open land with a herd of cattle grazing, and a handful of houses and barns, or 40-acres with a house and a barn and a shop and a cement driveway with a horse “pasture” that’s eaten down to dirt and weeds? The latter might seem extreme, but it’s what I drive past every single day on my way to the office at headquarters, and it breaks my heart to see so little respect for the environment by the same people who condemn us, their neighbors, for raising cattle.

Winter pasture.

Winter pasture.

Just a tip: if you want to hike, or ride your horse, or just see a ranch, write a letter or email to the manager (I would say call, but lots of ranches are sans reliable phone service!) and ask for access or a tour. They may say no, of course, as is their right, but it’s a better course of action than trespassing, which is not only illegal but will guarantee the denial of future access.


Alberta Sustainable Resource Development. (2008, April). Grazing Management Adjustments for Healthy Rangelands. Retrieved July 10, 2015, from ESRD:

Brady, J. (2014). Why Grass Finished Is Important. Retrieved July 27, 2015, from Brady’s Idaho Beef:

Center for Climate and Energy Solutions. (October 2009). Enteric Fermentation Mitigation. Retrieved July 27, 2015, from Center for Climate and Energy Solutions:

Explore Beef. (2009, April). Cattle Ranching and Environmental Stewardship. Retrieved July 15, 2015, from Explore Beef:

FAO. (2006, November 29). Livestock a major threat to environment. Retrieved June 15, 2015, from FAO Newsroom:

Johnston, G. (2012, 2 2). Why is beef losing ground to chicken? Retrieved June 15, 2015, from

Jones, M. (2014, February). Ways to Reduce Methane Production in Cattle. Retrieved July 26, 2015, from UNL Beef:

North American Meat Institute. (2011, March). The United States Meat Industry at a Glance. Retrieved July 7, 2015, from North American Meat Institute:

North Carolina State University. (2001, January 15). Scientists Find That Grasslands Can Act as Carbon Sinks. Retrieved August 19, 2015, from Science Daily:

United States Environmental Protection Agency. (2013). Overview of Greenhouse Gases. Retrieved 8 2015, July, from

United States Environmental Protection Agency. (2013). Overview of Greenhouse Gases: Methane Emissions. Retrieved July 8, 2015, from

USDA. (1996, August). Rangeland Health. Retrieved July 18, 2015, from Natural Resources Conservation Service Maryland:

Wiles, T. (2014, November 12). A new map shows rangeland health West-wide. Retrieved July 18, 2015, from High Country News:




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The Miracle Mineral Solution Sham and What You Can Do About It

I’m thrilled to share today’s article, written by another volunteer summer guest blogger, Mommy PhD (also known as Alison). As her stage name suggest, Alison has a PhD in Biology and Biomedical Sciences and post-doctoral training in neurotoxicology and epigenetics. Aside from being a mommy, she also currently works at Emory University as a post-doctoral fellow.

I follow Mommy PhD’s page on Facebook (you should, too!) and we’re in a few sciencey groups together, so I’ve been following along with her recent efforts to bring attention to what can only be described, in my opinion, as a group of terribly misguided parents engaging in horrific acts of (hopefully) unintended child abuse led and encouraged by a fanatic cult. This topic is a bit outside my usual realm of issues, but I asked Alison to write this post because, as a mother (and a human), I was appalled when I learned about it, and I think parents should be aware that this is happening and know of ways to help. Fair warning: some of the information and images below are a bit shocking – it turned my stomach, it might turn yours as well, but I hope bringing attention to this underground movement will help stop it. Thanks for reading, and thanks to Alison for her hard work.

——By Mommy PhD ——

Over the past few months, I have been working with an amazing group of people from all over the world to raise awareness about the use of Miracle Mineral Solution (chlorine dioxide, or CD, an industrial bleaching agent) as an enema to “cure” autism. Proponents of MMS claim that autism is caused by parasites and that bleach enemas remove these parasites and thereby “cure” autism. But what they think are parasites are really the lining of these children’s intestines that have been stripped away.

Some people blame the parents, but the real blame lies with the proponents of MMS who take advantage of parents who are searching for support and are overwhelmed with trying to help their child. In a way, as a mother, I can understand this. Parents will try anything to help their child. I have two kids and when it comes to protecting my children, I can turn into quite the mama bear. So when the proponents of MMS sell the false hope that autism can be cured, I can see how parents who can’t figure out what to do might fall for this. However, the proponents of MMS misrepresent science and flat out lie to support their lies. MMS has no benefit and can only cause harm.

  • There is no scientific basis for the use of MMS to treat autism (or anything else for which it is claimed to be used).
  • At the suggested doses, the chemicals in MMS are toxic. In fact, the most concerning effect observed in the toxicity studies of chlorine dioxide and sodium chlorite is neurodevelopmental delay.
  • Using untested, unproven and unregulated treatments on children is childhood experimentation. To experiment on children without appropriate regulation and approval is highly unethical.
  • There are many resources for support for parents and evidence-based information on autism. You can contact these places for recommendations in your area.
  • The authorities are beginning to crack down on those who sell and promote MMS and related products.

What is chlorine dioxide/MMS?

Chlorine dioxide/Miracle Mineral Solution is an industrial strength bleaching agent that can be used in very low concentrations as a water purifier. CD/MMS is sold as a 28 percent solution of sodium chlorite and an activator (an acid like citric acid). When these are combined, chlorine dioxide is formed. However, as an analysis carried out by an independent lab at the request of investigative journalists in the UK, this reaction is highly inefficient and most (90 percent) of the sodium chlorite remains in this form. This produces a solution with a concentration of chlorine dioxide and unconverted sodium chlorite many hundreds of times higher than the acceptable limit set by the EPA.  So when people use this product, as an enema or orally or as eye drops or however they use it, the toxicity results mostly from sodium chlorite.

Is chlorine dioxide a bleach?

Short answer: Yes.

Long answer: Yes. It is most definitely a bleach. See this article by Emily Willingham for a demonstration of what chlorine dioxide does to a navy blue cloth napkin.MMS is a bleach

Proponents of MMS will tell you that CD is not a bleach since it’s not household bleach (sodium hypochlorite). However, bleach is a general term that includes any compound that removes color. Chlorine dioxide is a bleach. It’s not household bleach, but it is most definitely a type of bleach.

Andy Brunning from Compound Interest created this graphic to demonstrate some of the many different chemicals that are classified as bleaches.


Who invented Miracle Mineral Solution and the CD Autism protocol?

MMS was invented by Jim Humble. He is not a doctor, yet claims that the CD/MMS protocols cure Ebola, malaria, HIV and other diseases. He invented this “cure” while on a gold mining expedition in Guyana in 1996. In online videos, he claims to be a billion-year-old god from the Andromeda galaxy, specifically from the Planet of the Gods.  He founded his own “non-religious” church (their choice of words, not mine), the Genesis II Church of Health and Healing, to protect himself and his “Ministers of Health” against legal action relating to his promotion of this protocol. They do not even try to hide that they formed this so-called church to protect themselves against prosecution and share information about how to avoid the authorities. This church looks very much like a cult.

Kerri Rivera is a “Minister of Health” within this church and has written a book describing her CD Autism protocol, which discusses CD/MMS given by enema or by drinking to “cure” children of autism.  She is also not a doctor. The justification for this protocol is that CD/MMS “cures” autism by removing the parasites (rope worms, not a real thing) that cause it. However, there is zero scientific plausibility that this treatment works. Autism is a not a disease to be cured. Research shows that autism is largely genetic. There is no link at all between parasites and autism.  What Kerri Rivera and other proponents of MMS say are parasites are really the lining of these children’s intestines that have been stripped away.

Intestinal parastiesFor comparison, here are some images on the left posted by parents of what falls out of their children after treating with MMS by enemas. Compare to the images on the right of actual intestinal parasites that infect the human gut. Worms have symmetry and structure, which the intestinal lining does not. What you see on the left are mixtures of intestinal mucus, undigested food, fecal matter and blood. They have no structure, no defined morphology, no symmetry. These are not parasites.

How do the kids react to being given MMS enemas?

Parents who are carrying out this protocol share their stories online. They share stories about their children crying in pain as they are held down and an industrial strength bleaching agent is forced into their rectums. They share pictures of the lining of their children’s intestines falling out, toenails falling off, and hair falling out. They share that their children stop showing emotion and have a loss of appetite. These are all signs of chronic poisoning and chronic abuse, but in these groups parents are congratulated for “curing” their children of autism. When parents post about disturbing symptoms their children are having in response to this “treatment”, the answer from the leaders is always – give more enemas.  These children are in pain but children trust their parents. This is an utter betrayal of that trust.

Is CD toxic at the dose recommended in the CD Autism protocol?

Yes. In fact, the FDA issued a warning about using this product in 2010:

‘FDA warned consumers not to consume or use Miracle Mineral Solution, an oral liquid solution also known as “Miracle Mineral Supplement” or “MMS.” The product, when used as directed, produces an industrial bleach that can cause serious harm to health. The product instructs consumers to mix the 28 percent sodium chlorite solution with an acid such as citrus juice. This mixture produces chlorine dioxide, a potent bleach used for stripping textiles and industrial water treatment. High oral doses of this bleach, such as those recommended in the labeling, can cause nausea, vomiting, diarrhea, and symptoms of severe dehydration.’

In 2000, the EPA did a comprehensive review of all the literature on the toxicity of chlorine-based disinfectants including chlorine dioxide and sodium chlorite. They used this review to determine safe levels for oral ingestion of these chemicals. They also determined the effects of toxic doses.

EPA Toxicology Review of ChlorineThe EPA concluded that oral ingestion of chlorine dioxide and sodium chlorite is safe below 0.03 mg/kg/day. This “reference dose” indicates the dose that is safe to drink every day of your life with no adverse effects. This means that a 20 kg child can safely ingest 0.6 mg (0.00002 ounces). While the EPA says these compounds are safe below these levels, this also means that above these levels, they are not safe. Doses of CD/MMS prepared as directed are 10,000 times higher than the EPA reference dose and 520 times higher than the WHO maximum allowable daily dose.

These are also oral doses. Doses given rectally (by enema) are likely to have a greater toxic effect as they are likely to be absorbed more readily. Rectal exposure was not tested by the EPA as it is not a common route of exposure for water disinfecting chemicals.

Perhaps the most shocking thing in this report is that the most consistent finding of long-term and developmental toxicity studies in animals was NEURODEVELOPMENTAL DELAY. So not only are people pushing a toxic substance, they are pushing a substance that is likely to cause the sorts of issues in children that they claim it prevents.

How do proponents of CD/MMS distort the toxicity data?

In CD/MMS groups, people will often cite this 1982 paper as evidence that the EPA says chlorine dioxide is safe. There are numerous problems with this claim that show the ways that proponents of MMS manipulate information and lie.

  • They are misrepresenting the source of the article. The article was not a publication of the EPA or carried out by EPA scientists. It was carried out by scientists at Ohio State University and was published in the journal Environmental Health Perspectives, which is published by the National Institute of Environmental Health Sciences.
  • The paper showed that drinking up to 5 ppm of sodium chlorite or chlorine dioxide for 12 weeks was safe. There is nothing wrong with the research in this paper. It clearly states that drinking half a liter (about half a quart) of a 5 ppm solution of chlorine-based disinfectants is safe.  What dose is this?  Assuming an average weight of 90 kilograms (almost 200 pounds) for an adult male, this is a dose of 3.5 MICROgrams/kg.
  • Lab tests show that most (90 percent) of the sodium chlorite in MMS remains unconverted yielding a 391 ppm sodium chlorite solution with very little chlorine dioxide. This given as directed translates to a dose of 312 mg/kg daily (for a 20 kg child). That’s MILLIgrams.  312 compared to 0.0035. The safety of a 0.0035 mg/kg dose tells us nothing about the safety of a 312 mg/kg dose.

Medical experimentation on children

Another huge issue with using the protocol on children is that using unproven treatments on children is medical experimentation. Doing this without proper approvals and oversight is a huge ethical issue. The National Institutes of Health have strict guidelines governing when it is ethically appropriate to use humans and children as subjects in medical studies. All human studies performed by medical professionals must be approved by the Institutional Review Board (IRB), a committee of scientists, doctors and community members, to ensure that human subject research is conducted in accordance with all federal, institutional and ethical guidelines. To use an unproven treatment without approvals on a child is experimentation and violates all of these guidelines.

Where can parents of autistic children find accurate information and helpful resources?

I imagine that parents find CD/MMS because they are looking for support and resources to help them navigate raising an autistic child. It’s unfortunate that they find information about CD/MMS and other fake cures being peddled to parents, instead of the excellent resources out there that provide accurate information and resources. Here are a few reputable sources for different kinds of information about autism.

What progress has been made to prevent the use of MMS?

Fortunately, over the past few months, we have made a lot of progress to stop these people from abusing more children.

  • Products relating to MMS were removed from Etsy and the US eBay site (new ones are popping up on eBay and people are continuing to report them).
  • Louis Daniel Smith in was convicted in US Federal court “for selling industrial bleach as a miracle cure for numerous diseases and illnesses, including cancer, AIDS, malaria, hepatitis, lyme disease, asthma and the common cold”. He set up a fake water purification business to purchase the chemicals and to attempt to hide his activities from authorities. He was convicted of conspiracy, introducing misbranded drugs with the intent to defraud and smuggling.
  • We held a small, peaceful protest at the AutismOne/Focus for Health Conference in Chicago, which I have written about before.
  • During the AutismOne (known for promoting dubious “cures” for autism) conference in May, the Illinois Attorney General, Lisa Madigan, served AutismOne regular Kerri Rivera with a subpoena and Kerri signed an Assurance of Voluntary Compliance, acknowledging that she has violated the Consumer Fraud Act and prohibiting her from giving seminars promoting CD/MMS and selling or promoting MMS in Illinois. Read more on this at Debunking Denialism.
  • There has been increased media coverage of this issue, especially by Phil Rogers and his team at NBC Chicago.

These are huge developments and the result of many months of hard work by many people. With the action by the Illinois Attorney General and the federal conviction of Smith, it is reassuring to see the authorities taking this seriously.

And, it’s not just in the US. In the UK authorities are also cracking down on the promotion and sale of these products and conferences promoting MMS in the UK have been cancelled after public outcry.

How You Can Help: Reporting products on Etsy and eBay

We were able to get Etsy to remove all CD/MMS related products from their site. We have made progress with eBay, but it’s been a little harder (their site is bigger and each country has it’s own site).  A few months ago, I emailed with them and they changed their filters so most of these products were blocked before they could be listed. Due to that, all products were removed from eBay, but there is a slow trickle of new products being listed as suppliers learn how the filters work.

However, it’s still fairly obvious that a 28 percent sodium chlorite solution with Jim Humble mentioned in the product description is not intended for water purification. There are also vendors selling only the citric acid activator. This is highly suspicious. Why would you need only citric acid activator? My suspicion is that when someone buys the activator, the order confirmation is followed by an email with instructions to purchase the sodium chlorite independently from eBay. We are continuing to monitor and report these products to eBay.

If you’d like to help report products, search eBay for chlorine dioxide, MMS, miracle mineral solution, Jim Humble, or sodium chlorite. At the lower right of the product page, below the “People who viewed this item also viewed” section, is a link to “report item”. (You do need to have an eBay login to report an item.) Report the item as a “prohibited and restricted item” and a “hazardous material”. Under detailed reason, select “pesticides and poisons.”

It’s been a good spring and summer for the fight against MMS. The momentum is with us and we continue to identify and report sellers and distributors to the appropriate authorities. We will continue our outreach to educate parents and to help them find the resources they need so they don’t fall for false hope. Hopefully, we can make MMS a thing of medical history, like leeches and bloodletting.


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Sol Survivor: Shedding light on sunscreen ingredients Part 2 of 2

(This is the second in a 2-part guest post by Jen Phillips. Jen holds a PhD in biology and is a Senior Research Associate at Westerfield Laboratory Institute of Neuroscience at the University of Oregon.)

Making sense of sunscreen controversies

Hello again!  In Part I of this series of posts, we explored the science behind sunlight, sunscreen and skin cancer.  That post left us with some pretty compelling reasons to cover up and slather on, but in this continuation we’ll be examining a few common claims out there that suggest sunscreen isn’t all it’s cracked up to be and may, in fact, be bad for you.  To put your mind at ease up front, there are no legitimate health concerns associated with sunscreen use, and there are demonstrable health benefits to regular application. So what’s all the fuss about?  Let’s take a look:

Does sunscreen use prevent cancer?

At first, this might seem like a silly question.  UV rays causes cancer, sunscreen blocks UV rays, therefore sunscreen must reduce skin cancer, right?  Sure, but scientific evaluation to back up this conclusion has had some mixed results.

sunscreen 2The biggest and most well-designed study to date was conducted in Australia, beginning in 1992.  The study included over a thousand participants, divided into an experimental group who applied SPF 16 sunscreen daily for four years, and a control group who used sunscreen at their own discretion. Initial results were reported after the four-year testing period, and additional data were obtained by tracking participants in both groups for another decade.  Overall, the study showed clear benefit of daily sunscreen use in prevention of squamous cell carcinoma (SCC), a benefit in prevention of Melanoma that was only noted at the end of the 10 year follow-up, and only a slight, statistically insignificant benefit in prevention of basal cell carcinoma (BCC.)

Why weren’t the results more spectacular, you might wonder, given the obvious correlation between UV radiation and skin cancer?  Based on its prevalence, one could hypothesize that BCC is easier to trigger than the other forms of skin cancer, and thus the SPF 16 sunscreen did not block enough UV rays to significantly reduce BCC rates. It’s also possible that UVA rays play a role in triggering BCC.  When this study was initiated in 1992, the sunscreen provided to participants—and indeed, all sunscreens on the market at that time—were UVB blocking only.

Still, even imperfect protection is better than none at all, right?  So using sunscreen would seem like a pretty straightforward choice.  Nevertheless, recent concerns over the safety of the products themselves have complicated the picture.

Does sunscreen disrupt hormones?

This claim is specific to oxybenzone–an organic UV filter that has been an active sunscreen ingredient for over 40 years.  The worry stems from in vitro studies showing that oxybenzone influences expression of estrogens and androgens in cultured breast cancer cells.  A study using mice also showed hormone related changes in uterine tissue when animals were fed oxybenzone daily.  Further potential for concern came from reports of oxybenzone being detected in urine and breast milk.

While it all sounds scary, the Paracelsus maxim (“the dosage makes the poison”) is important to keep in mind.  In vitro studies are notoriously lousy at predicting effects in functioning, multicellular systems like humans.  Further, the mice in the oxybenzone study were fed massive doses of the compound.  It would take several hundred years of daily sunscreen application to achieve similar exposure in humans, so it’s unlikely to be an issue for most of us.

What about the levels detected in urine and breast milk?  Well, oxybenzone is a popular ingredient in lots of products and materials beyond sunscreen. As such, it’s not surprising that it’s detectable in human excretions, and it’s not unique in that regard.  The key questions here are: are those levels attributable to sunscreen use and, more importantly, are those levels harmful?   To the first question, the urine study found no correlation between sunscreen use and oxybenzone levels.  To the second, a number of human studies specifically testing whether oxybenzone exposure from sunscreen use had any physiological effects showed no significant problems.  And finally, irrespective of the source of exposure, there have been no health problems of any kind linked to oxybenzone.  While it’s definitely valid to continue to monitor the chemicals in our environment, it’s also important to note that in nearly 5 decades of widespread use, no safety issues have come up.

Does sunscreen cause cancer?

This concern is primarily based on some in vitro studies showing that retinyl palmitate can generate biologically reactive molecules when exposed to UV radiation.  Retinyl palmitate isn’t a UV filter at all, but rather a Vitamin A precursor molecule that is a common additive to sunscreen formulas, as well as a great many other skincare and food products.  The factors generated when retinyl palmitate is exposed to light, called free radicals or reactive oxygen species, have a well-known potential to induce cancer.

Again, this a reasonable thing to test, but of the numerous studies conducted to assess the carcinogenic potential of retinyl palmitate, only a minority showed an effect, whereas most showed no adverse outcomes at all.  When weighed against the fact that widespread use of retinyl palmitate for years has resulted in no health problems, the few small in vitro studies suggesting harm are not convincing.

An additional cancer concern was raised by a couple of small studies that showed an increase in Melanoma in low-SPF sunscreen users compared to non-users.  The methods of these studies were relatively poor, compared to others that showed either no difference or a protective effect of sunscreen use.  Importantly the researchers didn’t evaluate other potential causes for the increase in Melanoma that they observed.  Stacked up against the better methodologies of larger studies, most particularly the comprehensive Australian study mentioned above, the data just don’t support a causative link between sunscreen use and Melanoma.

Is sunscreen toxic?

This concern arises from recent modifications to the inorganic sunscreen ingredients, zinc oxide and titanium dioxide, both of which filter UVB and some UVA rays.  Zinc oxide has been around for a while—you’ll probably recognize it as that opaque white stuff that beachgoers slather all over their noses.  Titanium dioxide is a more recent addition to the sunscreen arsenal, but is similarly pasty in appearance.

While such products are well-suited for small, high profile areas like the nose and cheekbones, their thick, pasty formulas are so difficult to spread that they’re not generally used for whole body protection, which is unfortunate because in addition to being great UV filters they’re also far less likely to cause skin reactions or allergies than some of the organic compounds.

To get around this problem, recent formulations use microsized” or “nanosized” titanium dioxide or zinc oxide mineral particles.  These preparations have the dual advantage of making the product easier to spread and less opaque.   However, the small size of these particles has raised concerns about their ability to penetrate the skin and reach toxic levels in the living cells beneath.  Fortunately, all the evidence indicates that these particles aren’t able to enter the body through the skin. Most were even tested on broken skin and showed no tendency to penetrate to the living cell layers.  This seems to be due, at least in part, to the fact that although the individual particles are indeed very small, they tend to aggregate together in solution, forming chemical bonds that keep them from moving around independently.

swing-1Does sunscreen cause vitamin D deficiency?

This concern seems reasonable on its face. Skin cells in the epidermis produce a vitamin D precursor that is activated by sunlight (by UVB rays, specifically). Block the sunlight, and you could potentially block vitamin D synthesis.  Studies have shown that sunscreen can indeed reduce vitamin D production.  Vitamin D screening is common in primary health care, and is now a cornerstone of the supplement industry, as well as a popular scapegoat for a wide range of maladies in the ‘wellness’ community.

There is a great deal of variation in the definitions of what might constitute a clinically normal vitamin D level in adults, so much so that experts don’t actually recommend routine screening at all.  However, legitimate vitamin D deficiency can lead to some well-characterized developmental problems, like rickets, so it is important to do due diligence when considering the effect of sunblock for children.  Fortunately, research has shown that the use of sunscreen doesn’t contribute to vitamin D deficiency.

Why the discrepancy? In short, it seems that no one is perfectly compliant when applying sunscreen.  A little sun exposure, literally 15-30 minutes a week, is all an otherwise healthy fair skinned person needs to synthesize sufficient amounts of vitamin D.  A few minutes in the sun without sunscreen, or maybe just on that one spot you couldn’t quite reach, appears to be enough.  This is borne out by both the lack of correlation between sunscreen use and vitamin D deficiency, and also the low incidence of rickets and other known outcomes of vitamin D deficiency, in the sunscreen-using population.

Are spray-on sunscreens safe?

A couple of years ago, the FDA announced that it was collecting more data on spray-on sunscreen, which at the time was relatively new to the market.  This was interpreted as an ominous development by some, and a number of unofficial advisories were issued about avoiding use on children, risk of inhalation, etc.  The FDA didn’t issue any sort of follow up on their findings, but based on the number of consumer bulletins about spray-on sunscreen on the FDA website, it seems pretty clear that there are no specific health concerns regarding the sunscreen part of the ingredients.  Much more emphasis has been placed on regulating the ‘dosage’, if you will, since it is applied so much differently than sunscreen lotion.  There are also a number of common-sense precautions that also apply to many other spray-on products. For example, it’s a terrible idea to apply an alcohol-based spray around an open flame, no matter what the other ingredients are.  It’s probably not a good idea to spray sunscreen into your kid’s face, any more than it would be a good idea to spray insect repellent or hairspray.  Inhaling aerosol products in lieu of air is typically an unpleasant experience.  However, aside from these fairly broad safety guidelines, there isn’t any specific reason to shy away from spray on sunscreen.

In summary,

-sunscreen continues to be recommended by healthcare professionals to prevent burns as well as to protect skin from premature aging and from cancer.

-sunscreen safety has been well established.  No health issues have been linked to sunscreen ingredients, despite extensive testing.

-sunscreen provides maximum protection when used appropriately—applying a thick, even layer and reapplying regularly.

One last thing:  the FDA requires sunscreen to be tested for stability and durability, and the expiration dates are usually around 3 years from the date of manufacturing.  These dates are backed by sufficient testing so as to be trustworthy, but also require the liberal application of common sense.  If your sunscreen is stored in extreme temperatures for a long period, for example, or if it changes consistency from one year to the next, it’s a good idea to replace it even if it’s not technically expired.

So, be smart about sun exposure, wear hats and water shirts when possible, seek out a broad-spectrum product with high SPF, slather up, and have a beautiful summer.  I’ll see you at the pool.


For more tips and information, see this sunscreen FAQ from the Skin Cancer Foundation

Also, see the Skin Cancer Foundation’s response to some of the recently renewed claims.



Burnett and Wang, 2011. Current sunscreen controversies:  a critical review. Photodermatology, Photoimmunity & Photomedicine. 27, 58-67

Jansen, et al., 2013. Photoprotection: Part II. Sunscreen: Development, efficacy and controversies. Journal of the American Academy of Dermatology 69(6). 867.e1-867.e14.

LeFevre, et al., 2015. Screening for Vitamin D Deficiency in Adults: U.S. Preventative Services Task Force Recommendation Statement.  Annals of Internal Medicine.162(2): 133-140.

Green, et al., 2011. Reduced melanoma after regular sunscreen use: randomized trial follow-up. Journal of Clinical Oncology  29(3):257-63.

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Sol Survivor: Shedding light on sunscreen ingredients Part 1 of 2

I’m very excited about this post for two reasons. One: it’s the first time I’ve recruited a guest blogger to write for It’s MomSense. This is cool to me because it means someone thinks my blog is influential enough to take their own (unpaid!) time to research and help us parents wade through the misinformation running rampant in parenting circles. The second reason is that this is a topic that I have meant to look into for some time. I am very fair skinned and burn easily and I’ve managed to pass this trait on to my red-headed son. I feel like I’ve spent every summer since he was born running around after him with a tube of sunscreen and a hat. Every once in a while there’s a small voice in the back of my mind asking if I’m actually doing him a disservice by routinely rubbing chemicals into the skin on the back of his neck. As a result, a while ago I added “sunscreen ingredients” to my running list of things to research and blog about.  Now that summer is in full swing and the sunscreen and I are best buds again, I’m glad to check this one off my list.

Because this topic is pretty involved, we decided to split it into two posts. So today and next week you’ll be hearing from Jen Phillips instead of me! Jen is the mom of two kids (one teen, one darn close) who has a PhD in biology.  She is a Senior Research Associate at Westerfield Laboratory Institute of Neuroscience at the University of Oregon. There she uses zebrafish to study the molecular genetics of human diseases. When she’s not hunkered down in a dark microscopy lab, she likes to romp in the sunshine with her family and dog. Jen plans to start her own blog at some point this year under the name Clutch Science. For now, you can follow her on twitter @ClutchScience. Here’s Jen to shed some light on sunscreen ingredients. Hope you enjoy. -Sara

Part 1:  The dark side of our closest star

Confession time:  I love the sun.  Swimming, running, working, reading, eating, lounging, it’s all better done outdoors, as far as I’m concerned.  But, as a fair-skinned woman, and mother of two lightly pigmented kids, I’d be foolish to ignore the risk involved, or to fail to take preventative steps to keep us healthy.  I am a stickler for sunscreen use, and, much to the chagrin of my children, I will not hesitate to halt a fun outdoor activity if it’s time to reapply.

It’s not news that sun protection is an important part of preventative health.  Ultraviolet radiation damages skin in a number of ways, the most serious of which can lead to cancer.   Recently, though, concerns about sunscreen ingredients have made headlines, raising questions about whether sunscreens are effective at skin cancer prevention and even whether the use of sunscreen carries inherent health risks.   **Spoiler alert:  sunscreen is safe and effective and you should use it with confidence.  If you’re interested in knowing more about the basis for the concerns and why you don’t need to worry, though, please read on!**

In the first of this two-part series, I’ll outline a bit of the biology and strategic chemistry behind the interactions with our closest star, in order to set the stage for discussing the most popular current controversies in Part II.

UV radiation:  what’s in a wavelength?

UVA_UVB raysUV radiation occupies the electromagnetic spectrum between visible light and x-rays.  The UV portion of the spectrum can be divided into quite a few subcategories, but the two that we’re most concerned about in sun exposure are known as UVA and UVB rays. UVB rays (also known as “burning rays”) can’t penetrate beyond our epidermis, or outer skin layer.  In addition to causing sunburn, DNA damage to epidermal cells by UVB rays is a driving factor in the development of skin cancer in light skinned people.  Until recently, UVA rays were alternatively called “Tanning rays” or “Ageing rays” depending on what product was being marketed.  In contrast to UVB rays, UVA rays penetrate more deeply, through the epidermis to the dermis below.  UVA rays cause inflammation and damage to structural proteins in the dermal layer, which have historically been associated with wrinkles and saggy skin.  More recently, UVA radiation has also been implicated in DNA damage that can lead to skin cancers.  This reclassification led the FDA to upgrade its caution on the use of tanning beds, by the way, which use primarily UVA wavelengths and were often advertised as a ‘safe’ form of tanning before the carcinogenic potential of UVA rays were better understood.  Now that we know better, let’s talk about skin cancer.

Your epidermis is showing

Cancer of any type arises through DNA mutations that alter cellular behavior.  UV radiation has been used in laboratories to induce mutations in cells for nearly a century.  Our skin is exposed to UV radiation on a regular basis, and while the pigments in darker skin offer protection against cell damage, those of us with fair skin have an increased risk of skin cancers as a result of sun exposure.

All skin cancers originate in the epidermis, which is composed of a tightly packed basal cell layer and a more mobile layer of cells known as squamous cells.  Our skin sheds and renews itself regularly, so the epidermis is constantly cranking out new cells that progressively travel from deep in the epidermis up toward the surface, changing shape as they go.

Skin cancers are classified into three broad categories according to the cell type affected:  Basal cell carcinoma, Squamous cell carcinoma, and Melanoma. Genetics and environment influence susceptibility, but in light-skinned people, sun exposure is a major risk factor for all three types.


Basal cell carcinoma (BCC) is the most common form of skin cancer in people of European and Hispanic descent, with nearly 3 million cases diagnosed each year.  It is also the most benign, as it rarely spreads to other cells beyond the original tumor site.

Squamous cell carcinoma (SCC) Is the most common form of skin cancer in dark-skinned people (who have a lower incidence of skin cancer overall because of the protection of higher melanin levels in their skin) and the second most common form in light-skinned individuals.  About 700,000 cases are reported each year.  SCC can be disfiguring if left untreated, and can, more rarely, spread to other regions of the body.

Melanoma, a cancerous overgrowth of melanocytes, accounts for only 2% of all skin cancers overall, but has the highest death rate of them all.  Melanocytes, which produce skin pigment, are found in the basal cell layer of the epidermis, but their developmental origins and cell biology are distinct from the other cells in this layer.  These differences, which amount to different gene regulation for things like cell division and migration, contribute to the uniquely aggressive nature of malignant melanomas.

Considering the varied ways that things can go wrong in living skin cells, it’s important to understand what preventative steps we can take.  Limiting sun exposure during the peak hours is always a wise recommendation, as is the use of hats and clothing to cover the most exposed areas. But as lots of outdoor activities aren’t compatible with those guidelines, protection that can be applied directly to the skin is a great advantage.

How does sunscreen work?

All available sunscreen products contain UV filters that absorb, reflect, or diffuse UV radiation.  Ingredients with these properties are classified as either organic (carbon-based), or inorganic (based on other elements).

Lots of chemistry goes into choosing compounds that make the best sunscreen ingredients.  Compounds are tested for the particular range of UV wavelengths they can intercept and for durability.  The best compounds will block a wide swath of the UVB spectrum without being easily degraded.  No one wants to wear sunscreen that has to be reapplied every 15 minutes, right?  These qualities must then be weighed against the utility of the ingredient in a product designed to be applied to human skin:  Does it stink? Does it have a texture or color? Does it irritate skin or cause allergies?  Are there other safety or toxicity concerns?  FDA approval is required for all sunscreen ingredients, and their standards for safety testing are quite rigorous.  In fact, a number of organic sunscreen ingredients approved for use in Europe haven’t made the grade as far as the FDA is concerned.

What about SPF?

Sun Protection Factor of a product, or SPF, is usually framed for marketing purposes as the amount of time you can spend in the sun before burning when using the product versus time spent in the sun without it.  More specifically, the SPF value is the quantifiable effectiveness of the UVB filtering capacity of any given ingredient—or combination of ingredients. This is a non-linear numerical scale.  An SPF of 15 corresponds to blocking about 94% of UVB rays, while an SFP of 30 increases blocking capacity to 97%.

Note that SPF rates the product’s effectiveness of blocking only UVB rays. Since learning more about the damage that UVA rays can create, Sunscreen formulas have expanded to include UVA filtering alongside UVB (SPF-rated) protection.  Again, there’s a bit of a difference between how we do things in the US vs. abroad.  Other countries have a rating system (out of 5 stars) to indicate the strength of the UVA blocking compounds.  The FDA hasn’t implemented any such system yet.  The presence of UVA filters added to the SPF-rated UVB compounds in US products isn’t quantified, and only the words “broad spectrum” let you know that your sunscreen contains both UVA and UVB blocking ingredients.

To sum up this overview of the science behind sunscreen, both UVA and UVB rays can have detrimental effects on the health of your skin, so in addition to limiting exposure in as many ways as are practical, having a good sunscreen product on board is essential.

However, for the past several years a number of controversial warnings about the safety and effectiveness of sunscreen products have emerged.  In Part II of this series, I’ll examine those claims one by one to determine if there is really cause for concern.

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