The Cancer Chronicles (22 page)

The other side of the energy equation is physical exercise, and in modern times
people are able to lead more sedentary lives. “You and
I are having a very pleasant conversation sitting here,” Riboli said. “At another time in another place we might be having this conversation walking in a field. We are moving less and eating more.” Exercise is not, however, a simple matter of burning off pounds. Exertion makes you hungry and you may respond by consuming at least as many calories as you expend. More important may be the effects of exercise on keeping
insulin and other hormones under control. Lower your weight and exercise more. “Twenty years ago these were just ideas,” Riboli said. Now EPIC is seeking scientific support. The work is only beginning.
An official statement from EPIC promises to explore the
complex
interactions between genetic, metabolic, hormonal, inflammatory, and dietary factors. More knots to untangle.

I told Riboli I was feeling even better about having walked to his office all the way across Hyde Park. He laughed and as I put away my notebook he took me on a brisk walk down the hall, out of the building, and beyond the gate of the hospital grounds, until we were standing on the side of Praed Street. He pointed up to a window in the old hospital building, the one to
Alexander Fleming’s office. He told me a story that has become part of the legend—how Fleming had accidentally left the window open, allowing the spores of
penicillin fungus to contaminate the agar plate. That detail may be apocryphal, but it is an encouraging reminder that a great medical discovery can come suddenly through an act of serendipity.

As I walked toward the Tube station—I’d exercised enough for the day—I thought of how it can never be so easy with
cancer. The infectious diseases we have defeated were each caused by a single agent—an identifiable enemy that could be killed or vaccinated against. With cancer we would have to seize control of a whole slew of factors, including the mishmash of symptoms arising from imbalances in energy metabolism. And the biggest risks will always lie beyond our grip: old age and entropy. Cancer is not a disease. It is a
phenomenon.

What left me feeling more optimistic is what EPIC might find in the future. In coming years as more people in the study come down
with cancer, researchers will be able to analyze their blood in minute detail to see what it was like years or even decades before they got sick. With technologies like
nuclear magnetic resonance, they will be able to scrutinize thousands of blood chemicals, looking for signs that might portend the later onset of cancer. This is a very different way of doing medical research. A scientist traditionally begins by posing a hypothesis—based on an observation or a statistical study or a simple hunch. Maybe a high level of a vitamin increases or lowers the risk of some cancer. Then you go looking for evidence. With resources like those at EPIC, connections may emerge that no single mind would have come to suspect. The result could be reliable tests that give early warning for a malignancy the way high cholesterol warns of
heart disease. Maybe by then there will be something we can do about it.

One surefire carcinogen
Riboli and I didn’t talk about is
radioactivity. Here the mechanism is straightforward: The unstable nucleus of an element like
radium shoots out particles and rays with so much energy that they can tear through molecules, break chemical bonds, and wreak all kinds of cellular hell. Emanations this forceful are called
ionizing radiation (atoms stripped of electrons are ions). If the radioactive particles don’t strike a gene head-on, inducing a mutation, they might leave
a wake of corrosive free radicals in the cell’s cytoplasm—a condition called
oxidative stress than can damage the
genome indirectly. Shifting into panic mode, the mangled cell might
send signals to neighboring cells, inducing more stress and genomic shock. Most of the exposure we receive from this carcinogen comes from natural sources. The greatest contributor is said to be radon rising from the soil below.

Ever since I had my house
tested for the gas two decades ago, registering a modest amount, I had paid little attention to the warnings. Radon, like carbon monoxide, is an invisible, odorless, silent killer—albeit one that works slowly as mutations mount year by year. Of the approximately 160,000
lung
cancer deaths each year in the United
States, the Environmental Protection Agency has said that 21,000, or
13.4 percent, may be
radon related. What you don’t often hear is that for about 90 percent of those deaths
smoking is also a factor. Through all the years of my life, I had smoked a grand total of maybe ten cigarettes—and none during the last twenty-five years. Still, as I began to learn more about cancer, I felt a need to conduct another radon test—this time in a room where I had recently been sitting for weeks writing this book.

It had been an unusually cold winter in
Santa Fe. Access to my second-story office requires traversing an outdoor staircase. It’s an easy and picturesque commute but sometimes it involves shoveling snow. For that and other reasons I had taken to working downstairs in a room that was built, like many in old Santa Fe, over a dirt crawl space. Two walls of the room are about six feet below ground level and built from adobe bricks molded from the same dirt that lay beneath the floor. For weeks the weather outside had been too cold for opening windows, and I had latched shut a door between the office and the hallway to hold in heat. The conditions, in other words, were likely to result in stagnant air and maximum readings of radon gas.

I ordered a test kit, placed it on the desk, and forty-eight hours later mailed it to the laboratory named on the instruction sheet. This time the results that came back were more than quadruple what they had been before: 22.8 pico
curies per liter.
The EPA’s scale, correlating radon levels with risk, topped off at 20, and remedial action was recommended at just 4
picocuries per liter. A curie is approximately the amount of
radiation produced by a gram of radium, so a picocurie is one-trillionth of that: 2.2 nuclear disintegrations per minute. As radon rapidly decomposes, it shoots out
alpha particles (
clusters of two neutrons and two protons) and breaks down into smaller elements, which float through the air emitting alpha particles of their own. They don’t travel far—alpha rays can be stopped with a sheet of paper—but because of their massiveness they deliver a heavy blow. The radon gas itself is readily expelled from the lungs,
but the daughter particles, inhaled with every breath, can stick in the wetness and irradiate cells. Every minute in every liter of that stagnant air, fifty of these submicroscopic explosions were occurring. The EPA chart that came with the test kit informed me that if one thousand people who have never been smokers are exposed to 20 picocuries per liter throughout their entire lives, thirty-six of them would be likely to get lung cancer. Another way of saying it is that the lifetime risk is 3.6 percent. (For smokers exposed to that much radon the odds are seven times greater.)

As I thought about these numbers, I began to feel a tightness in my chest. I imagined my lungs heavy with a miasma of cold, radioactive air. Compared with the astronomical amount of atoms in one breath of air, the fifty radioactive events occurring every minute is a vanishingly tiny proportion. And only a fraction of the shrapnel, these alpha particles, would strike lung tissue and cause genetic mutations. Most mutations, I reminded myself, are harmless. Our DNA is mutating all of the time. Cells have evolved mechanisms to repair broken DNA or to destroy themselves if the damage is too great. Of all the mutations that occur in a
genome only certain combinations might trigger a cancer, and only if many other things go wrong. But for all of those reassurances there still was a palpable risk.

The test had been done under such airtight conditions that the reading was bound to be abnormally high. Half a year later, in warmer weather, I measured again. This time I placed the detector in the bedroom (where
Nancy and I had slept for seventeen years). I opened and closed doors and windows according to my usual routine. The measurement this time, closer to normal conditions, was much lower—7.8 picocuries. A third reading, in the hottest part of summer, when fans were circulating air through the house, came in at just 0.8 picocuries—way below the national mean. The average of my three readings was 10.5 picocuries (a risk of 1.8 percent). My odds were looking better and I wondered if I could lower them a little more.

The EPA numbers are based on the assumption that people
spend, on average,
70 percent of their time at home—nearly seventeen hours a day. That would be high for someone commuting to a full-time job. I work at home but most often I am upstairs, where my exposure would presumably be much less. Radon comes from the earth and is eight times heavier than air. With no interior staircase or forced-air heating, I felt safe in my office aerie. When I am downstairs I am often in parts of the house where radon levels are also probably lower. (Maybe I will buy more test kits.) To allow for all of that, I cut my estimated exposure—reducing it by one-fourth seemed reasonable—and then I cut it again. I’ve lived in the house for only about a third of my life. Dividing by three brought the level down to 2.6 picocuries—below the EPA “action level”—and my risk to about 0.3 percent.
The chance of a nonsmoker getting lung
cancer sometime in life is usually put at around 1 percent or less. If so, then living in this comfortable old house might have raised my odds to something like 1.3 percent, from a minuscule risk to a somewhat less minuscule one. But I guess that is a self-centered view. Spread across the population that would account for a lot of cancer.

My calculations were rough. If I wanted to estimate more precisely, I would have to consider every other place I have lived. I had a basement bedroom when I was a child, but I’d lived on the fourth floor of a row house in Brooklyn and the eighteenth floor of a high-rise in Manhattan. It would be possible in theory to calculate long-term exposure with
a laboratory analysis of my eyeglasses. When alpha particles strike carbonate plastic lenses they leave tracks—memories of
radiation exposure. The tracks—there are typically thousands per square centimeter—can be translated into radon readings. There is also
a method using ordinary household glass. Radon decay products are deposited on mirrors, picture frames, and cabinet windows and can become incorporated into the glass. By measuring the amount that has accumulated and considering other variables, epidemiologists can estimate how much radon people have been exposed to over many years—not just in their current homes but for
as long as they have owned the objects.

As I thought about all the microscopic wallops I might have
incurred, I wondered where the EPA had gotten its figures in the first place—so many picocuries per liter corresponding to so many lung cancer deaths. It’s not like you can lock a thousand people in a basement and then wait for some of them to get cancer. The story began in the 1970s when
houses in Grand Junction, Colorado, built on top of tailings salvaged from
uranium mines, were found to have elevated levels of radon. At great expense the radioactive fill was removed and replaced, but the radon readings remained high. Then came a much reported incident with
a construction engineer named
Stanley Watras. He was working in 1984 at a
nuclear power plant in Pennsylvania. As the plant neared completion,
radiation alarms were installed, and they sounded whenever Watras passed by. The reactors, however, were not yet operating and there was no fissionable material in the plant. The source of the contamination turned out to be his house, which measured as high as 2,700 picocuries. You didn’t need to build on uranium tailings to have radioactive air. Homes across the country were found to register positive for radon, and it was coming from the natural soil. Radon has been with us from the start.

In an attempt to gauge how threatening the exposure really was,
epidemiologists began conducting case control studies, comparing radon levels for people who had contracted lung cancer with people who had not. Early results were inconclusive—some detected a small effect and others did not.
A study in Winnipeg, which had the highest radon levels of eighteen cities in Canada, found no influence on lung cancer. Other researchers
compared the average radon levels of different geographical areas. Again no association was found. A nationwide survey reported
a negative correlation, as though breathing radon somehow provided protection. Or else
the study was flawed. Some critics suspected that the results were
skewed by an inverse connection between smoking and the amount of radon measured in homes.
Perhaps cigarette smoke interfered with the radon monitors, or smokers were more likely to occupy older, draftier houses or to open more windows.

Getting better numbers would require either very large populations
or very high
radon levels—the
hundreds to thousands of picocuries per liter that can be found in underground mines. Looking for answers, researchers studied
lung
cancer rates among uranium miners in Colorado, New Mexico, France, the Czech Republic,
Canada (an area on the shore of Great Bear Lake had the evocative name Port Radium), and Australia (Radium Hill). They studied miners of other ores in Canada, China, and Sweden—altogether 68,000 men. Of those, 2,700 had died from lung cancer. That is about 4 percent. There were confounding factors to consider. Most of the miners were believed to be smokers but the data on
how long or how often they had smoked was sparse or nonexistent. Miners are also exposed to diesel fumes, silica, and other dust, which might have synergistic effects. Laborers breathe harder than someone cooking dinner or reading a book in bed.

Doing their best to adjust for these complications,
a committee of the
National Research Council began analyzing the numbers and quantifying the relationship between radon and lung cancer. They assumed that it must be linear—that one-tenth the exposure leads to one-tenth the risk. Not all toxicologists believe that is true, proposing instead that there is a threshold below which
radiation causes no damage. But the mainstream view is that even the smallest amounts are potentially harmful. With marathon feats of statistical calculation, the numbers for the miners were adjusted downward to estimate the risk from the far lower exposures found in homes. That was the basis for the chart distributed by the EPA and included in my test kit.