Sunday, November 14th, 2010
Each year, we hear that people are gaining weight and that chronic health problems like obesity, heart problems, and diabetes are on the rise. It’s commonplace to ascribe these trends to personal lifestyle choices, such as the lack of exercise and diet, as well as the increasingly pervasive nature of fast food and processed, high-sugar foods.
However, there may be additional risk factors that are harder to control, such as genetics, and—as a provocative new article in PLoS One (open access) suggests—birth order. Specifically, first-born children might be more prone to these kinds of chronic health issues later in life:
Recent work has suggested that birth order may be a non-modifiable risk factor for obesity. Current evidence suggests that first-born infants grow faster than later-born infants. Dunger et al. suggest that the in-utero growth of first-born babies may be restrained as they have lower birth weight and accelerated post-natal catch-up growth, both of which are risk factors for obesity and cardiovascular and metabolic diseases, in adult life. However, whether first-born individuals have elevated metabolic risk in adulthood remains unknown. A recent study found that first-borns had a 4-fold risk of increased fat mass in early adulthood compared to later-borns. Neither of these studies evaluated the magnitude of metabolic risk induced by such greater weight and adiposity.
…Here we investigate the associations of birth-order with metabolic phenotype in early adulthood using data from a birth cohort of Brazilian young men. We tested two hypotheses. First, we wanted to confirm that first-born status was associated with low birth weight and faster infant growth. Second, we tested the hypothesis that metabolic risk was increased in first-borns compared to later-borns.
What did they find? What implications might their work have for public health given the kinds of global population changes we expect over coming decades?
Sunday, October 10th, 2010
Thomas Rogers at Salon.com has a review of Devra Davis’ new book, “Disconnect: The Truth About Cell Phone Radiation, What the Industry Has Done to Hide It, and How to Protect Your Family“.
The apparent bottom line for cell phone safety:
The full article is worth reading. Below are a few excerpts of the review and Rogers’ interview with Davis:
In “Disconnect,” Devra Davis, a scientist and National Book Award finalist for “When Smoke Ran Like Water,” looks at the connection between cellphones and health problems, with some disturbing results. Recent studies have tied cellphone use to rises in brain damage, cheek cancer and malfunctioning sperm. She reveals the unsettling fact that many new cellphones now come with the small-print warning that they are to be kept at least one-inch from the ear (presumably for safety reasons) and many insurance companies refuse to insure cellphone companies against health-related claims. Most troubling of all, science has shown that children and teenagers are particularly susceptible to cellphone radiation, raising questions about its effects on coming generations.
What to you is the most compelling evidence that links cellphones to brain cancer?
The brain cancer connection is in fact a very complicated one. Cancer can take a long time to develop. After the Hiroshima bomb fell, there was no increase in brain cancer for 10 years, even 20 years afterward. Forty years later, there was a significant increase in brain cancer in people who survived the bombing. Now, for studies of people who have been heavy cellphone users (defined as someone who has made a half-hour call a day for 10 years), there is a 50 percent increase in brain cancer overall. And among the heaviest users there’s a two- to fourfold increased risk.
We’ve only really been using cellphones for 10 years. Isn’t it a bit early to be drawing these kinds of conclusions?
Well, that’s actually not true. Heavy use of cellphones in the United States is a very recent phenomenon for the general population. In the year 2000, fewer than half of us regularly used cellphones. Now almost all of us do. If there’s a 10-year latency, we still have to wait another five years in the United States to see any general population impacts.
You have to look at all of the evidence and not simply wait for proof of human harm or sick people or dead people. If the debate becomes, “Do we have sufficient proof of human harm?” that means we’re waiting another 20 years. That means we will potentially have an epidemic before we act to prevent harm. Now, some people could be very cynical and say, look, brain cancer is relatively rare so even if it doubles or quadruples it’s still rare. But it’s also, at this point, mostly incurable.
Why are young people so much more at risk?
Their brains are not fully protected with myelin. Myelin is a kind of fatty sheath that goes around neurons [brain cells] and helps to enhance judgment and a whole bunch of other things, like impulse control. Their skulls are also thinner, and a thinner skull admits more radiation. We now know that the young brain doesn’t mature until the mid-20s, later in boys than girls. We need to be much more vigilant about protecting the young brain because it is more vulnerable. We know that from work that’s been done on lead and a number of other agents.
If this research is really as convincing as it seems to be, then why hasn’t it created a widespread uproar?
Well, it has in France. Bills passed both houses of the French national government this spring that ban the marketing and creation of phones uniquely for children. It’s also had an impact in Israel, a country that is very sophisticated in its use of radar and microwaves, and Finland, both of which have issued warnings.
But think about the fine print warning that comes with BlackBerry Torch. It says, If you keep the phone in your pocket, it can exceed the FCC exposure guidelines. What’s that supposed to tell you? It sounds like that phone cannot safely be put in your pocket — well, where do they expect people to keep them?
….The book also describes the aggressive push-back by people affiliated with the cellphone industry against scientists whose findings point to safety concerns — including, in one case, a campaign to discredit someone’s findings by accusing them of manufacturing evidence. It’s pretty explosive stuff.
I think it might have started out as nothing more than companies wanting to make profits, and wanting to keep their products in a positive light. Companies are allowed to make profits; I’m not opposed to that. And I imagine people genuinely thought these kinds of dangers from radiation weren’t possible, because the physics paradigm [at the time] said it wasn’t. But it has since been morphed into something worse. Now even the insurance industry is listening to scientists. Many companies are no longer providing coverage for health damage from cellphones.
We need to be more sophisticated as a society in using experimental data where we have it. We have experimental data on sperm counts. We have experimental data on brain cell damage. We have experimental data on biological markers that we know increase the risk of cancer. These are the same debates that went out over passive smoking, over active smoking, over asbestos, over benzene, over vinyl chloride. They said we don’t have enough sick or dead people. The consequence was to continue exposing people. Is there anybody in the world who believes we should have waited as long as we did?
Photo credit: liber
Thursday, October 7th, 2010
There’s a new paper in this week’s issue of Science that suggests that growing a landscape mixed with genetically modified (GM) Bt corn and non-GM hybrid varieties of corn can be mutually beneficial to all corn farmers.
Why? They argue that the populations of GM corn knock down the populations of insect herbivores enough that, on a landscape scale, this effect spills over to nearby farmers growing non-GM corn, which raises yields and profits:
[W]e estimate that cumulative benefits for both Bt and non-Bt maize growers during the past 14 years were almost $6.9 billion in the five-state region (18.7 million ha in
2009)—more than $3.2 billion in Illinois, Minnesota, and Wisconsin, and $3.6 billion in Iowa and Nebraska. Of this $6.9 billion total, cumulative suppression benefits to non-Bt maize growers resulting from O. nubilalis [European corn borer] population suppression in non-Bt maize exceeded $4.3 billion—more than $2.4 billion in Illinois, Minnesota, and Wisconsin, and $1.9 billion in Iowa and Nebraska—or about 63% of the total benefits.
They suggest that the populations of non-GM corn also benefit the Bt corn farmers because the non-GM corn maintains a genetically diverse population of insects, helping prevent the evolution of herbivores resistant to Bt corn.
These results are interesting and —if they hold—could be an example of how GM crops bring environmental and social benefits. A good outcome for all.
However, there are a couple of important things to consider:
(1) The notion of mixing crop types to minimize herbivory is the one of the fundamental tenets of traditional agroecology and organic agriculture, but instead of relying on GM crops, it could be done with a mix of hybrid crop varieties that doesn’t risk the potential environmental side effects of Bt corn or other unexpected outcomes of GM crops. This is a major value judgment. Does having one GM crop and a few dominant corn varieties count as diversity when the Midwest becomes a giant sea of maize? As I explain in #2 below, probably not. Could we achieve the same kind of insect pest management using a diversity of non-GM crops? Yes—it happens all the time in midwestern organic farms. Multi-crop organic farming is often more labor intensive than industrial agriculture, making the food produced more expensive. But do we only care about cheap food?
(2) I’ve lived in southern Minnesota, where it’s a giant rotating monoculture of corn and soybeans. If you look at Figure 1 in this paper, you will see that 50-75% (or more) of the corn grown in many regions of states like Iowa, Nebraska, and Minnesota is Bt corn. When so much of your landscape is Bt corn, the evolution of resistance to Bt is most likely inevitable, as we saw in a previous post with the use of Roundup-ready crops like soybeans, which are often grown in rotation with Bt corn in these regions. Acknowledging this fact of life, EPA recommends mixing GM and non-GM corn in an effort to delay the evolution of resistance, not prevent it:
To delay evolution of resistance, the U.S. Environmental Protection Agency (EPA) mandated that a minimum 20 to 50% of total onfarm maize be planted as non-Bt maize within 0.8 km of Bt fields as a structured refuge for susceptible O. nubilalis. Use of non-Bt maize refugia is an important element of long-term insect resistance management.
…Sustained economic and environmental benefits of this technology, however, will depend on continued stewardship by producers to maintain non-Bt maize refugia to minimize the risk of evolution of Bt resistance in crop pest species, and also on the dynamics of Bt resistance evolution at low pest densities and for variable pest phenotypes.
Hutchison, W., Burkness, E., Mitchell, P., Moon, R., Leslie, T., Fleischer, S., Abrahamson, M., Hamilton, K., Steffey, K., Gray, M., Hellmich, R., Kaster, L., Hunt, T., Wright, R., Pecinovsky, K., Rabaey, T., Flood, B., & Raun, E. (2010). Areawide Suppression of European Corn Borer with Bt Maize Reaps Savings to Non-Bt Maize Growers Science, 330 (6001), 222-225 DOI: 10.1126/science.1190242
Photo credit: Ian Hayhurst
Wednesday, September 29th, 2010
Water security is making a bit of a splash this week. CNBC ran this story on the water crises in western U.S. states, where the region is possibly closing in on a day of reckoning, as described by Felicity Barringer in the NY Times, and creating a climate of pessimism among some western water managers.
The scientific community is also weighing in. C.J. Vörösmarty and colleagues published a review paper in this week’s issue of Nature in which they evaluate the worldwide risk of water security and threats to aquatic biodiversity (edited slightly to remove citations and statistics):
We find that nearly 80% (4.8 billion) of the world’s population (for 2000) lives in areas where either incident human water security or biodiversity threat exceeds the 75th percentile. Regions of intensive agriculture and dense settlement show high incident threat, as exemplified by much of the United States, virtually all of Europe (excluding Scandinavia and northern Russia), and large portions of central Asia, the Middle East, the Indian subcontinent and eastern China. Smaller contiguous areas of high incident threat appear in central Mexico, Cuba, North Africa, Nigeria, South Africa, Korea and Japan. The impact of water scarcity accentuates threat to drylands, as is apparent in the desert belt transition zones across all continents (for example, Argentina, Sahel, Central Asia, Australian Murray–Darling basin).
What is the disparity of risk between rich vs. poor nations?
Most of Africa, large areas in central Asia and countries including China, India, Peru, or Bolivia struggle with establishing basic water services like clean drinking water and sanitation, and emerge here as regions of greatest adjusted human water security threat. Lack of water infrastructure yields direct economic impacts. Drought- and famine-prone Ethiopia, for example, has 150 times less reservoir storage per capita than North America and its climate and hydrological variability takes a 38% toll on gross domestic product (GDP). The number of people under chronically high water scarcity, many of whom are poor, is 1.7 billion or more globally, with 1.0 billion of these living in areas with high adjusted human water security threat.
They also argue that as wealth increases in a nation, the apparent ability to deal with water security issues improves, leading to the perception that threat level is declining:
Contrasts between incident and adjusted human water security threat are striking when considered relative to national wealth. Incident human water security threat is a rising but saturating function of per capita GDP, whereas adjusted human water security threat declines sharply in affluent countries in response to technological investments. The latter constitutes a unique expression of the environmental Kuznets curve, which describes rising ambient stressor loads during early-to-middle stages of economic growth followed by reduced loading through environmental controls instituted as development proceeds. The concept applies well to air pollutants that directly expose humans to health risks, and which can be regulated at their source. The global investment strategy for human water security shows a distinctly different pattern. Rich countries tolerate relatively high levels of ambient stressors, then reduce their negative impacts by treating symptoms instead of underlying causes of incident threat.
Biodiversity threats from river use appear to be significant globally:
The worldwide pattern of river threats documented here offers the most comprehensive explanation so far of why freshwater biodiversity is considered to be in a state of crisis. Estimates suggest that at least 10,000–20,000 freshwater species are extinct or at risk, with loss rates rivalling those of previous transitions between geological epochs like the Pleistocene-to-Holocene.
And what about future prospects?
We remain off-pace for meeting the Millennium Development Goals for basic sanitation services, a testament to the lack of societal resolve, when one considers that a century of engineering know-how is available and returns on investment in facilities are high. For Organisation for Economic Co-operation and Development (OECD) and BRIC (Brazil, Russia, India and China) countries alone, 800 billion US dollars per year will be required in 2015 to cover investments in water infrastructure, a target likely to go unmet. The situation is even more daunting for biodiversity. International goals for its protection lag well behind expectation and global investments are poorly enumerated but likely to be orders of magnitude lower than those for human water security, leaving at risk animal and plant populations, critical habitat and ecosystem services that directly underpin the livelihoods of many of the world’s poor.
…with a not-so-comforting conclusion:
Left unaddressed, these linked human water security–biodiversity water challenges are forecast to generate social instability of growing concern to civil and military planners.
Vörösmarty, C., McIntyre, P., Gessner, M., Dudgeon, D., Prusevich, A., Green, P., Glidden, S., Bunn, S., Sullivan, C., Liermann, C., & Davies, P. (2010). Global threats to human water security and river biodiversity Nature, 467 (7315), 555-561 DOI: 10.1038/nature09440
Photo credit: suburbanbloke
Monday, September 27th, 2010
Genetically modified organisms (GMOs) are back in the news. A few days ago, NPR featured a couple of blog posts (here and here) considering whether the new GMO “supersized” salmon will be harmful to aquatic ecosystems.
A concern with GMOs is that—like the early adoption of pesticides—potential risks are being borne by the environment and consumers as we experiment with new species. There’s a lot of potential for GMOs, and I hope that they all end up being harmless. But there are potential downsides too that we are not able to assess very well at this point. And we may be creating problems that we are not even aware of yet.
As more data come in, it’s not always an encouraging outlook. A couple of recent examples:
Case #1: We saw a few months ago how weeds that were supposed to be eliminated by the agricultural herbicide, Roundup, are now evolving resistance to the chemical, meaning that Roundup-ready soybeans and other crops no longer work as designed.
Case #2: In this week’s Early Edition of the Proceedings of the National Academy of Sciences, Jennifer Tank and colleagues examined what happens to transgenic corn residue (old crop parts left on fields that are not harvested). One of the main transgenic varieties of corn is known as “Bt corn.” Bt stands for the name of a microbe—Bacillus thuringiensis—that makes a protein toxin that destroys the functioning of guts in some insects. Scientists have figured out how to move the Bt gene, and hence Bt toxin manufacturing capacity, from the bacteria to corn plants, thereby conferring general insect herbivore resistance to this crop (the main pest being the European corn borer).
This team asked: What happens when corn stalks, cobs, and leaves end up in streams and rivers throughout the Midwest? Their answer is eye-opening:
Widespread planting of maize throughout the agricultural Midwest may result in detritus entering adjacent stream ecosystems, and 63% of the 2009 US maize crop was genetically modified to express insecticidal Cry proteins derived from Bacillus thuringiensis. Six months after harvest, we conducted a synoptic survey of 217 stream sites in Indiana to determine the extent of maize detritus and presence of Cry1Ab protein in the stream network. We found that 86% of stream sites contained maize leaves, cobs, husks, and/or stalks in the active stream channel. We also detected Cry1Ab protein in stream-channel maize at 13% of sites and in the water column at 23% of sites. We found that 82% of stream sites were adjacent to maize fields, and Geographical Information Systems analyses indicated that 100% of sites containing Cry1Ab-positive detritus in the active stream channel had maize planted within 500 m during the previous crop year. Maize detritus likely enters streams throughout the Corn Belt; using US Department of Agriculture land cover data, we estimate that 91% of the 256,446 km of streams/rivers in Iowa, Illinois, and Indiana are located within 500 m of a maize field. Maize detritus is common in low-gradient stream channels in northwestern Indiana, and Cry1Ab proteins persist in maize leaves and can be measured in the water column even 6 mo after harvest. Hence, maize detritus, and associated Cry1Ab proteins, are widely distributed and persistent in the headwater streams of a Corn Belt landscape.
Who cares? Streams and rivers are the breeding grounds to many insect species, including dragonflies, mayflies, and damselflies. If there are toxins floating in these aquatic ecosystems that are good at killing insects, there is risk of disrupting food webs, including potential changes to bird species as well as many important recreational and sport fish that dine on insects:
Once maize detritus enters stream channels, this carbon source degrades rapidly via a combination of microbial decomposition, physical breakdown, and invertebrate consumption, and that energy may fuel stream food webs. Maize detritus in agricultural streams decomposes in ∼66 d …. Therefore, the material that we found during our synoptic survey had entered these streams relatively recently. Maize detritus is rapidly colonized by stream-dwelling invertebrates, and growth rates of invertebrates feeding on nontransgenic decomposing maize are comparable to those feeding on the deciduous leaf litter commonly found in forested streams
Perhaps this means that the Bt toxins might break down quickly and pose less harm? Doesn’t look like it:
Our data demonstrate that long after harvest, Cry1Ab is present in submerged Bt maize detritus; thus, stream organisms may be exposed to Cry1Ab for several months.
It’s also interesting to learn that low or no-till conservation tillage practices may exacerbate the corn residue inputs because greater material left on fields is susceptible to washing away:
The dried detritus left on fields after harvest, as part of conservation tillage, enters headwater streams as a result of surface runoff and/or wind events occurring throughout the year. During heavy precipitation, overland flow is the likely mechanism transporting this material to stream channels.
It may not even be a matter of leaving less residue; the toxins also appear to be draining through the soils:
Our results from tile drains indicate that tiles may be a mechanism by which Cry1Ab leached from detritus on fields or from soils can be transported to streams.
Cry1Ab released from root exudates or decaying maize detritus moves vertically through soils and can be detected at the base of 15-cm-long soil profiles for up to 9 h.
Their conclusion? An illustration of how little we know at this point:
The question of whether the concentrations of Cry1Ab protein we report in this study have any effects on nontarget organisms merits further study.
Jennifer L. Tank, Emma J. Rosi-Marshall, Todd V. Royer, Matt R. Whiles, Natalie A. Griffiths, Therese C. Frauendorf, and David J. Treering (2010). Occurrence of maize detritus and a transgenic insecticidal protein (Cry1Ab) within the stream network of an agricultural landscape Proceedings of the National Academy of Sciences : 10.1073/pnas.1006925107
Photo credit: snake.eyes
Saturday, February 27th, 2010
Environmental Working Group (EWG) has updated their information on cell phone radiation and potential health risks.
As I alluded to in a previous post, conducting human health risk analyses for things like cell phone radiation exposure is difficult because it’s hard to determine how much exposure is too much, and it takes years to see what health effects might show up.
The research below suggests that links between cell phone radiation and health are now becoming evident.
And with more than 4 billion cell phone users worldwide (2/3 of the human population), we are unintentionally conducting one of the largest epidemiological studies of all time.
Learn more from EWG:
Monday, February 1st, 2010
Over the past few years, there have been a couple of major approaches for dealing with climate change:
Of course these are not mutually exclusive, but they might as well be given the way they have played out on the political stage.
With a lot of people down on political solutions to deal with climate change, strong advocates of the latter approach may now gain the upper hand. Folks like Shellenberger and Nordhaus have been arguing that green energy needs to be produced as quickly and cheaply as possible—forget all of the games with cap and trade or carbon taxes. Tom Friedman has also argued the need for swift action on energy, while also endorsing political solutions like carbon taxes.
If you look for areas that are gaining or have the potential to gain traction, there seem to be two levers that may work:
Both of these general concerns have attracted Republican support for green energy and climate change mitigation, including Senator Lindsey Graham (R-SC).
This may be a signal of potential game changers and the clearest path forward that we’ve seen in awhile.
Thursday, December 24th, 2009
One of the outcomes of climate warming is that species will have to move to remain within climatic zones that match their physiological tolerances. Some common examples include the northward migration of boreal forest species into areas that are currently tundra and the upward migration of mountain species.
As Scott Loarie and colleagues note1 in this week’s Nature (subscription required), we often think of mountain ecosystems as being particularly threatened because alpine species have nowhere to go.
To analyze this challenge, they looked at the spatial gradients of temperature across land masses of the world. These data indicate how temperature changes over a known distance (temperature gradient = degrees C per kilometer).
Then, they used climate model model projections to determine how fast the temperature of a region will change (warming rate = degrees C per year).
By dividing the warming rate by the temperature gradient, they determined what they called the temperature velocity (kilometers per year)—which is basically represents how fast you (or another species) needs to move along the earth’s surface to maintain a constant temperature (check this division for yourself to see how the units cancel).
What did they find?