How do you distinguish between hazard and hype in environmental health?

There are times that I find myself extremely envious of toxicologists in the 1950-1980s. Mercury, lead, cigarette smoke, PCBs, etc., all of these were the important toxicants of the era, chemicals and toxic exposures that have such clear adverse health impacts. Of course this is because I am idealizing what it must have been like to be studying toxicology back then, but I am imagining a conversation at a medical department that would go something like this, “Hey, I don't think that developmental exposure to mercury is going to have any effect.” “Oh really? Let me show you.” Then a series of very simple experiments are conducted with amazingly clear results and an extremely high impact publication is produced that continues to be cited for decades. Next week, “Oh, I don’t think cigarette smoke has any bad effects.” “Oh really? Let me show you.” And repeat.

Today, in my view, the most important research question in the field of toxicology is, what are the effects of low-level toxicant exposures? Particularly when the exposure is nearly ubiquitous. (See a recent study that suggests fetal BPA exposure to be nearly ‘universal’ http://pubs.acs.org/doi/abs/10.1021/es402764d)

If we look at the field of toxicology as having two halves to it, the first half being everything that has been studied up until now, and the second half being what will come from now until the field is dead, the first half of toxicology, in my view, was about defining the toxicities of chemical exposures at high doses. Although things such as arsenic, lead, and mercury have been known to be toxic going back to ancient times, the actual investigations into the biological mechanisms and pathological outcomes have not been defined until the 20^th century, where modern biological research techniques we able to be employed. Today, toxicologists often times don’t have the luxury to study the effects of clearly toxic chemicals at high doses; we need to address the concerns that pertain to our public, the chemicals that we are exposed to, at the doses that we are exposed to.

The reality is that due to the toxicologists, the research, and the public outcry and environmental policy that followed this period of investigation, human exposure to many of the major hazardous compounds has largely decreased. But, new chemicals have been introduced, while old toxicants continue to elude complete avoidance.

This brings us to the major question of the future of toxicology, how do you deal with low-level exposures? What are the effects? And, how do you know what exposure is truly hazardous, versus simply hype?

Nearly every day, when I scan the news, I will come across an article about environmental exposures, health, and toxicology. People care about this stuff, but it’s difficult to truly communicate what is something to be concerned about. In trying to understand truly hazardous versus hype, there is rarely a more difficult case than low pesticide exposure and the organic vs traditional food debate.

In a paper published just recently in PLoS One, a graduate student in the UW Dept. of Environmental and Occupational Health Sciences (Cynthia Curl) looked at organic produce consumption and socioeconomic status in a large cohort, (Congrats to Cynthia! this is a great publication).

http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0069778

What she found, in many ways, was exactly what you would expect. You are more likely to be eating organic produce if you are: a woman, younger, from a more economically strong an liberal city, have a higher income, more educated, employed, and have closer access to supermarkets.

Although these results are what most people would likely hypothesize, and this data supports this fantastically, I was most struck by the percentages of those saying that they eat organic produce. In total, 40% of their population say they ‘sometimes, often or always consume organic produce’, reaching as high as 61% for those between the ages of 45-54 (the youngest age group).

This strikes me as a large number, and what it says to me is that roughly half of the population (I bet if those between the ages 18-45 were included, they would have an even higher rate) makes the conscious choice to purchase organic produce. So why would half the public make this choice?

Although this question may sound simple, there are many reasons why someone would choose to buy organic produce vs non-organic produce, and people buy organic produce for different reasons. Regardless of the reason someone would buy organic produce, any walk through the supermarket produce section will reveal that organic produce is typically more expensive than traditional produce. Whatever the reason someone chooses to buy organic, he/she did some sort of cost benefit analysis and came to the conclusion that organic produce is worth the added cost. You guys may remember when there was a flurry of excitement and anger when a group from Stanford published a report saying that organic produce was no ‘healthier’ than normal produce.

http://www.nytimes.com/2012/09/04/science/earth/study-questions-advantages-of-organic-meat-and-produce.html?_r=0

Here’s the actual study: http://annals.org/article.aspx?articleID=1355685

The study was a systematic review, in which they extracted data from every single publication on the topic thus far, to combine the data in a more complete statistical analysis. These types of studies are considered an excellent way to look at everything that has been done on a topic so far, which helps to eliminate a ‘single study bias’, where conclusions may be erroneously made following a single study. The review looked at organic vs traditional foods in terms of nutritional value (i.e. vitamins, minerals, etc.) as well as presence of toxic chemicals (arsenic, lead, mercury, as well as pesticide residues). They also reviewed the few studies to date looking at organic vs traditional food consumption and risk of clinical disease. Their conclusions were simple, 1) there is no nutritional difference between organic and traditionally grown foods, 2) there are slightly increased pesticide residues in traditional food produces, and 3) the studies looking at clinical health outcome thus far do not show any adverse health effects. Overall, they report that organic foods are not ‘healthier’.

On my Facebook feed, which I admit has way more toxicologists and public health people than likely the normal Facebook feed, people were freaking out. The general sentiments were, “obviously we don’t eat organic for more nutrients” and “they don’t know what the potential health risks of low level pesticide exposures are”.

But what’s interesting, as the authors’ note in this publication, is that it is a widespread belief that organic produce has more nutritional value. And although the extremely low level pesticide residue on certain traditionally grown produce may have some extremely low level effect, the current investigations into this have proved null. The reality is that we do not have the strong evidence to say that eating organic foods vs traditionally grown foods will result in a better clinical outcome. Now, I’m not saying that eating organic is not worth it, the lesser environmental impacts and sustainable farming practices that are encouraged in organic farming is reason enough, but there is simply not strong enough evidence to say that eating traditionally grown foods is bad for you. What we do have is evidence that eating a large amount of fruits and vegetables daily will dramatically reduce one’s risk of disease, for reasons still unclear (as someone who loves to study antioxidants, we can’t just say this is due to antioxidants). And what we should be encouraging more than anything is to eat fruits and vegetables daily, regardless of organic or not.

The organic vs traditional food argument is the perfect example of the challenge between separating the reality vs the hype in environmental health and toxicology. Most pesticides are extremely toxic to humans. They are a challenging class of toxicants because they are designed to be toxic, and they typically target the exact same biological mechanisms that are shared between insects and humans. But, again here comes the issue of low level exposures, what about these trace residues or produce?

In toxicology, we love to quote Paracelsus, the 15^th century physician who is famously attributed to the phrase, “the dose makes the poison”. In this quote, he reasoned that it is the dose that distinguishes what makes a remedy from a poison. This is a cute saying, and it makes an easy slide when lecturing on the basics of toxicology, but I feel that we often times forget this in toxicology. In my view, the dose truly does make the poison, and in saying so, a pesticide at a high dose, has about as much in common with the same pesticide at a low dose as any other toxic chemical, which is to say it doesn’t have much in common at all. When people discuss the potential health implications of low level pesticide exposures, they tend to discuss mechanisms that have nothing in similarity to the biological mechanism of action that is seen in a high dose pesticide exposure, in my view, this makes it essentially a different poison. Because the known toxic mechanism of high level exposures is not at play in these low level exposures, any potential toxicity would be considered very different from the high dose toxicity, and it’s very possible that these low level exposures do not have a real effect. Currently, this is the view of the FDA, and I have a hard time coming to any other conclusion with the data published so far.

So what should we think about organic vs traditional foods? How do we deal with a low level exposure of something that we know is toxic at high doses? I don’t know if I have a clear answer, but I wanted to make two points that are quite opposed to each other. This is why I am still confused about how to address these concerns.

1) We need to stop focusing on markers, and start focusing on real clinical outcomes.

Often times we overly convince ourselves that we know why certain things are beneficial and why certain things are not. For example, as I mentioned above, we know that eating a large amount of fruits and vegetables will dramatically reduce our risk of a myriad of diseases. But if you ask someone, why are fruits and vegetables are good for us? You will likely get an answer like, “oh the antioxidants!” And as a result, food products will advertise their antioxidant content, creating labels like “Vitamin Water”, claiming to be beneficial because of the antioxidant content. But the reality is that the antioxidant supplement trials have been a complete, and I mean complete, disaster. Millions and millions of NIH dollars later, we can say that taking antioxidant supplements should be avoided. Taking high dose antioxidants increases the risk of cancers in most populations and we cannot see any benefit in terms of most clinical outcomes. What we know is that eating a diet rich in fruits and vegetables, which contain high amounts of antioxidants, will result in longer lifespan and reduced risk of disease; not, eating high amount of antioxidants will result in longer lifespan and reduced risk of disease. As discussed in the Book Oxygen, Nick Lane argues that many of the toxins in fruits in vegetables, naturally produced to prevent bugs from eating them, may actually be mildly toxic to us as well, stimulating an adaptive response that may prove to be protective in the long run. What this says is that we still don’t know for sure why fruits and vegetables are good for us, so focusing on a marker, say looking at antioxidant content, will not allow us to know the full story. Applying this to pesticide residues on fruits and vegetables, without data to support this, we cannot say that traditional foods are less healthy for us due to trace pesticide residues, we can’t say this without actual clinical outcomes.

Here's the link to Oxygen, which is essentially a 300 page complex review article on redox biology, but I highly recommend it for those interested.

http://www.amazon.com/Oxygen-Molecule-World-Popular-Science/dp/0198607830

2) Does it even matter if we know something is actually good or not? Or is our ‘gut’ feeling about something being ‘good’ or ‘bad’ actually better?

If we take the traditional vs organic food argument, many people have come to the conclusion that organic is ‘better’, and it really doesn’t matter what the actual clinical or analytical data says. People buy organic for many different reasons, and it may just feel better to buy organic, is there anything wrong with that? Although I may not be convinced that organic foods are actually a way for us to improve health or reduce our risk of disease, I do believe that the practice of organic farming has its heart in the right place. Perhaps our world would be better with an entirely organic food production system, so if people believe that there will be health benefits to buy organic, regardless of if it is true or not, this may have a benefit to our community. This same argument would apply to the current debate on GMO labeling, although I do not believe there is any health risk to eating GMO foods, perhaps the sustainability and better food practices that come with non GMO foods are worth it to discourage the practice. Although understanding how the public feels about a particular concern in the absence of any supporting data is a tricky situation, I’m starting to believe that when the heart is in the right place, believing in a benefit that may not be there, while simultaneously supporting an industry that has good practices, may turn out to have alternative benefits in the long run.

The point at which this becomes a problem is when someone avoids needed medication because of an unsubstantiated belief in an alternative treatment, I may write more about this in the future.

Overall, our ability to distinguish between the truly hazardous and seriously hyped risks of environmental exposures is a challenge that has important implications. The media reports on these topics don’t help in distinguishing the two, and somehow we expect the general public to have a full understanding of the risks and benefits of certain practices, even when there is no consensus between experts in the field. We need to do better at coming to conclusions ourselves before we can expect the public to understand these risks, and when we do, we need to vigorously engage with the public to help disseminate important public health information.

Chad Weldy