It is also misleading to note the relative increase in risk—25 percent— but not the actual size of the risk. In 1970, there were a little more than 13 cases of cancer for every 100,000 children. It then rose to a peak of 16.8 cases per 100,000 children—meaning the annual risk of a child getting cancer was 0.0168 percent. Now, put all this information together and it sounds like this: In 1970, the risk of childhood cancer was very small. It increased until 1985 but has remained stable ever since. Despite the increase, the risk continues to be very small. “Cancer in children is rare, accounting for only about one per cent of cases,” notes the Progress Report. That is hardly the description of an epidemic. In addition, the rate of childhood cancer deaths has fallen steadily over the last three decades. In 1970, about 7 children per 100,000 were killed by cancer; thirty years later, the rate had dropped to 3.
American figures are almost identical. According to a 1999 publication of the U.S. National Cancer Institute, childhood cancers rose from 1975 until 1991 and then declined slightly. In 1975, there were about 13 cases per 100,000 children. In 1990, that had risen to 16. The death rate dropped steadily, from 5 per 100,000 children in 1975 to 2.6 two decades later.
British statistics show the same trend. From 1962 until 1971, the rate of childhood cancer cases was flat. It then rose steadily until 1995 but appears to have stabilized. In 1971, there were 10.1 cases per 100,000 children. In 1995, there were 13.6. The death rate fell steadily throughout this period, from 7.8 per 100,000 children to 3.2. Medicine is steadily breaking cancer’s grip on children.
Still, the increased risk of children getting cancer may have stopped rising, but it did rise. What could have caused that rise if not chemical contamination? Here, it’s very important to remember that numbers are only as good as the methods used to calculate them. All statistics have strengths and weaknesses. Cancer data are a perfect demonstration of that universal truth.
There are two ways to measure how much cancer there is in society. One is simply to count deaths caused by cancer. Most such deaths are unmistakable and they’re carefully recorded, which makes death stats a reliable way to track the disease’s prevalence. Or at least they were in the past. Treatments have improved dramatically in recent decades and so, increasingly, victims survive who would not have in the past. As a result, cancer death rates may decline even if the actual cancer rate doesn’t, and so death statistics tend to underestimate the reality.
The other way of tracking cancer is to use what are called incidence rates. These are based simply on the number of people diagnosed with cancer, and they would seem to more accurately reflect the real level of cancer in society. But incidence rates can be tricky, too. If physicians get better at diagnosing a cancer, the number of diagnosed cases will rise even if the actual prevalence of cancer doesn’t. Even changes in how bureaucrats file paperwork and collect numbers can artificially push up incidence numbers. What really throws the numbers off, however, are screening programs. Many forms of cancer—including breast, prostate, thyroid, and skin—are known to produce cancers that just sit there. They don’t do any damage, don’t progress, and don’t cause any symptoms. Those who have them may live out their lives without ever knowing of their existence. But screening programs—such as blood tests for prostate cancer and mammograms for breast cancer—can detect both the aggressive and the irrelevant cancers and so when they are introduced, or improved, incidence rates soar. When that happens, it doesn’t mean more people are getting cancer, only that more cancer is being uncovered.
So to get a sense of what’s really happening, experts look at both death and incidence statistics. If they rise together, cancer is probably on the rise. They’re also reliable indicators if they go down together. But they often point in opposite directions—as they did with childhood cancers in the 1970s and 1980s. To sort things out when that happens, experts have to investigate from every angle and consider the relative weight of the many factors that may be pushing the numbers one way or another. And even then there are likely to be some uncertainties because that’s the best science can do.
And that conclusion seems to be the answer to the rise in childhood cancers that ended in the mid-1980s. “Improvements in the efficiency of systems for the diagnosis and registration of cancer may have contributed to the increase in registration rates,” noted Cancer Research UK. “It has also probably become easier to track and record the diagnosis of new patients as treatment has become more centralized. The amount of real change, if any, in the underlying incidence rates is not clear.”
Variations between sexes, populations, and countries make it difficult to generalize about cancer in adults. Even more important, cancer isn’t really one disease, it is many. But still, the broad outlines are clear.
The age-adjusted rates of deaths caused by most types of cancer have been falling for many years in developed countries. (An important exception is smoking-related cancers among those groups in which smoking rates have yet to fall.) As for incidence rates, they rose in the 1970s, rose more rapidly in the 1980s, but then leveled off in the last ten or fifteen years. It is not a coincidence that the period that saw the most rapid increases— the 1980s—also saw the introduction of major screening programs. There is a consensus among researchers that a big chunk of the rise in incidence rates over the last three decades was the result of better screening, diagnosis, and collection of statistics.
And, in any event, the rise in incidence rates has generally stopped. In the United States, the numbers for the last several years—both incidence and death rates—have been remarkably encouraging. Even the total number of deaths caused by cancer has fallen, which is pretty amazing considering that the American population is growing and aging. Summing up the trends, Bruce Ames says, “If you take away the cancer due to smoking and the extra cancer due to the fact that we’re living longer, then there’s no increase in cancer.”
Advocates of the chemicals-are-killing-us claim respond with one final sally. We don’t know, they say. “The worrying reality is that no one really knows what effects these chemicals have on humans,” reads a Greenpeace report. “We are all unwittingly taking part in an unregulated global experiment that needs to be stopped,” says the World Wildlife Fund.
There has been an enormous amount of scientific study of chemicals over the last half century, but it’s still true that a great many synthetic chemicals have not been rigorously analyzed, either separately or in their combined effects with other chemicals. There really is lots we don’t know. That’s particularly true in case of the raging controversy over the endocrine disruptor hypothesis—the idea that trace amounts of synthetic chemicals such as bisphenol A can throw the body’s hormones off balance, lowering sperm counts, causing cancer, and maybe much more. The hypothesis first got widespread attention in the mid-1990s, and scores of scientists have been studying the issue for more than a decade, but still the science remains contradictory and unsettled. Regulatory agencies in Europe, the United States, and Japan have reviewed the evidence on bisphenol A and decided there is no reason to ban the chemical, but the investigation goes on. Slow and complicated: That’s science at work.