Archive for January, 2010
More than a billion people worldwide smoke tobacco. With a 20-fold greater risk of developing lung cancer than nonsmokers, plus increased risks of other types of cancers, choosing to smoke represents the most significant carcinogenic exposure confronting public health professionals today. A recently completed study published in Nature (se below) reports on the sequencing of DNA from a small-cell lung cancer victim. Tobacco smoke deposits hundreds of chemicals in an individual’s airways and lungs including numerous mutagens. The investigators have used massively parallel sequencing to illuminate the distinctive mutations associated with exposure to cigarette smoke carcinogens, as well as the signature of DNA repair activities.
The investigators didn’t speculate about the policy implications of this work, but things that come to mind for me include better early detection of pre-cancerous conditions, genomic therapies that intervene on a macromolecular level and an airtight method for denying someone health insurance coverage for lung cancer treatment because of self-inflicted tobacco carcinogenesis.
One of the worrisome statements made in the discussion section was that, on average, lung cancer develops after 50 pack-years of smoking (where a pack-year is 7,300 cigarettes, representing the number smoked in a pack a day for a year), or an average of one mutation for every 15 cigarettes smoked, which could potentially transform a normal cell into a cancerous one that eventually clones into a tumor.
There are a couple of epidemiological modeling papers cited for that conclusion that should be looked in on later, but the 50 pack-years assessment provoked a bit of an oh-shit moment, because if I’m understanding the number properly, 50 pack-years is around a pack a day for one year; the dose-response relationship is cumulative, so the same risk would be associated with half a pack a day for two years, and so forth. Tobacco contains a lot of other carcinogens other than mutagens, which initiate a carcinogenic response; these other carcinogens are promoters, which accelerate the growth and development of a tumor. So, even if you’ve only currently a “light” smoker, you’re probably still screwing yourself health-wise; even if you quit years ago, you may have macromolecular or cellular injury now, that will eventually turn into lung cancer, but it just hasn’t progressed to the that you’re experiencing adverse effects. It’s just another reason for not smoking at all or stopping at the earliest instance possible, in order to preserve your health (and insurance).
Pleasance, E.D. et al. 2009. A small-cell lung cancer genome with complex signatures of tobacco exposure. Nature. 463, 184-190 (14 January 2009) http://www.nature.com/nature/journal/v463/n7278/full/nature08629.html
Huffpo is info-smack for me. I really should dry out from it, but. . . well, what can you say? Maybe the smack example is a little much, so perhaps it’s like Pop-Tarts, tasty and somewhat filling, if completely un-nutritious. . . .
But sometimes, I get something mildly usable from it, at least enough to keep up the blogging rate. Today’s example is a post in Huffpo about the city in the nation with the highest home foreclosure rate, along with 16% unemployment: Stockton, CA.
I remember Stockton. Thirty years ago, I lived in Sacramento just about an hour north of Stockton, first working for the State of California regulating pesticides, then working for a couple of environmental consulting firms. I passed through Stockton more times than I can remember, on the way to the Bay Area – taking I-5 to I-205 and through the Altamont Pass was longer than I-80, but I would gladly drive the extra 70 miles, if I could go 80 mph all the way and avoid being stuck in traffic. Stockton was also a waypoint when driving south to the San Joaquin Valley, to work sites where I could observe and monitor workers using pesticides, measuring their exposure and collecting data to figure out methods for reducing those exposures.
I was just starting to see the growth in the Valley towns when we left California – tens of thousands of people who bought homes in places such as Stockton, Modesto, Merced, Patterson, and commuted two-plus hours per day one way to jobs in the Bay Area. I don’t think I have to read further to figure out what’s happened – the jobs in the Bay Area are starting to dry up, and there’s nothing locally to replace them. . . .
I’ve managed to miss all of this. We left California in 1995 for opportunities elsewhere, and it feels as if we dodged a bullet. It’s difficult for me to imagine what would be so desirable in a job that would make it worth driving 60 miles, one way in heavy traffic, while living in a garden spot such as Stockton. Don’t get me wrong, I could live there, if I had a job in town. Driving to Hayward to work every day? No way. But that’s me. In the end, I’m relieved that we got out when we did. California – forty million people can be wrong.
Considered to be a probable human carcinogen through inhalation, formaldehyde for several years has been the subject of a risk assessment being conducted by EPA, as well as a candidate for development of emissions standards under the Clean Air Act. Formaldehyde is used in manufacturing of building materials, and the offgassing from new building materials is a source of formaldehyde exposure in indoor air for potentially millions of people.
There have been several signal events related to formaldehyde which have occurred within the past few years. Temporary housing units used by FEMA to house people rendered homeless from Hurricanes Katrina and Rita were found to have concentrations of formaldehyde in air at levels that were sufficiently high that public health officials were concerned about potential health risks to the occupants. Recently published epidemiological studies of workers indicate that exposed to formaldehyde is associated with an increased incidence of leukemia (formaldehyde is already thought to be associated with an increased risk of nasal cancers in workers). Senator David Vitter has held up nomination of a key EPA deputy administrator over the formaldehyde risk assessment, insisting that the risk assessment undergo review by the National Academy of Sciences, a step that would delay any regulation of formaldehyde emissions by a few years. Finally, the California Air Resources Board finalized air toxics control measures for the manufacturing of some building materials containing formaldehyde.
Beyond the fact that formaldehyde has been recognized as a human cancer risk and a widespread indoor air contaminant for over two decades, an argument can be made that the existing regulatory frameworks will not produce real reductions in formaldehyde exposure for many years. It is not simply a matter that more information is needed to make a decision. Collecting and analyzing more information can in certain cases create more opportunities to create doubt and distraction. The problem then is defining the kinds of information, messaging and framework that would mobilize enough power to effect changes; in this case, reengineering the manufacturing of building materials to “green” the formaldehyde out of them.
This involves either molding the views of decision makers or creating an enormous groundswell of public opinion. . . . [To be continued]
I ran across this story in Science Progress, a “progressive science blog” which comes across as earnest, involved and. . . dull. Dull and earnest meant that I couldn’t get too worked up about this screed by Chris Mooney about climate change denialism, which mentions the Pew Center statistic that a declining fraction of the American public is concerned about climate change.
However this does raise a good question about why, with the majority of the scientific community that is knowledgeable about the topic of climate change issuing alarms, is climate change risk communication so ineffective. I look at climate change, and see nothing but ways to make capital flow so that lots of people can make money. There’s some kind of a lesson about how being smart and committed about a topic isn’t necessarily enough to galvanize interest and concern about it.
As always, Peter Sandman has some sensible things to say about the problem of climate change apathy and precaution advocacy. However, I recall a few months back something on his blog about him planning to retire soon. I wonder who’s going to be picking up the slack here.
Wired Magazine online just published its top scientific breakthroughs in 2009, and there are two environmental health ones in the list: the sensor that can “smell cancer”, or in other words, can detect exhaled volatile organic compounds that are early biomarkers of potential lung tumors (blogged about earlier) and bisphenol-a. Wired cites a report from the Knight Science Journalism Tracker, which reports on a recently published paper in Human Reproduction about evidence of adverse male reproductive effects in workers exposed to high levels of bisphenol-a (BPA). Male factory workers at a facility in China with BPA exposure have “strikingly high rates of erectile dysfunction and impairment of ejaculation”. The study is on my reading list, but if this proves to be a real adverse effect, maybe it will be the thing that finally stirs some action to address BPA exposure. That or boost stocks in PDE-5 inhibitors.