Dr. Thomas W. Kensler '70, a professor at Johns Hopkins Bloomberg School of Public Health, spoke about the spreading cancer epidemic and possible solutions to this growing global problem on Feb. 4. It was the first lecture of the semester in a series on global health issues sponsored by the Diversity and Social Justice Project. Kensler's talk focused on efforts to identify risk factors and prevent exposure to carcinogens. His current work focuses on the growing cancer rates in China.
Kensler began by describing the magnitude of the worldwide cancer problem as well as the causes and biology of the disease. Cancer currently accounts for 13 percent of deaths worldwide, or about seven million people annually. By 2030, this figure may rise to 20 million deaths annually. Of these deaths, the majority currently and will continue to occur in developing nations. Most affected will be Africa, Southeast Asia and parts of South America. By 2050, two-thirds of all cancers will occur in Southeast Asia, partially as a result of population growth in these areas. Cancer tends to have a late-life onset, occurring most frequently in persons over the age of 45. It can take three to four decades for this cancer to grow from a single cell to billions of cells in the body. Kensler sees this relatively slow growth rate as an opportunity for interference before the cancer spreads. Still, he says the most effective way to eliminate the growing cancer threat is prevention before the cells have a chance to form. He cited lung, liver and breast cancers to discuss the upward trend of cancer prevalence in the developing world and also offered some possible solutions to these growing afflictions.
Kensler identified three main causes of cancer. Tobacco use ties directly to the cause of about one-third of cancer, poor dietary habits accounts for another third, and infectious diseases directly contribute to about 20 percent. Of these, he emphasized tobacco as one of the greatest contributors to risk factors that could and should be decreased. Tobacco probably contributes to about 87 percent of the incidence of lung cancer. Not only do its carcinogens increase the risk for lung cancer, but it increases the risks for most other forms of cancer as well, including oral and esophageal. He pointed out that quitting smoking can decrease the risk of cancer by half in five years.
However, in countries such as China, which currently accounts for 33 percent of all tobacco use and where tobacco production is the country's largest industry, few steps have been taken to decrease the tobacco consumption throughout the country. Kensler found that in some rural areas, up to 50 percent of the annual income was spent on cigarettes. With such a high prevalence and a general lack of public knowledge about the potential side effects of smoking, China has a rapidly growing lung cancer incidence that will only worsen as the cancer develops in the current generations over the next several decades.
The incidence of lung cancer is further affected by the outdoor pollution associated with rapid urbanization of the developing world. Also, indoor use of biofuels, such as cow dung, in these developing nations further increases the amount of inhaled carcinogens. While Kensler pointed out that this last contributor is difficult to control on a large scale, he said that tobacco consumption and outdoor pollution should both be handled as matters of public policy. He emphasized the role of governments and world health organizations in spreading the message to control these factors.
Kensler also connected infectious agents to the high incidence of liver cancer in China and throughout the world. Infectious agents account for about 26 percent of all cancers in the developing world and only about eight percent in the developed world. Specific to Kensler's research, he and his American and Chinese colleagues found that exposure to the hepatitis B virus and aflatoxin, a dietary toxin from mold, increased the risk of liver cancer 60 times. Exclusive exposure to either of these diseases only slightly increased the incidence of cancer. Kensler recognized that by at least preventing one of these infectious agents from affecting the body, the incidence of liver cancer could be greatly reduced.
Currently in Africa and Southeast Asia less than 10 percent of all inhabitants are immunized against hepatitis B. Kensler identified economic constraints (the HBV vaccine is relatively expensive) as well as a lack of healthcare infrastructure in these developing nations as the principal cause of the lack of immunizations. As a result, Kensler sought a cost-effective and efficient method to help prevent the carcinogens in aflatoxin from settling in the body, as proper harvesting and food storage methods that prevent the mold from growing seemed difficult to teach on a large scale.
He and his colleagues found that certain vegetables, such as Brussels sprouts and broccoli, had an anticarcinogenic effect and that the active agent also dissolved well in water. They harvested these plants, heated them into tea, and found that they successfully decreased the effect of carcinogens on the body. Kensler believes these anticarcinogenics may offer one solution to the growing liver cancer epidemic, as the treatment is relatively easy to procure and administer. However, Kensler also recognizes that using Brussels sprouts in tea may not work as well in other areas, like Africa, where they are not used as commonly as in Southeast Asia.
Finally, Kensler discussed the growing incidence of breast cancer, both globally and in China. He described breast cancer as a primarily Western form of cancer that was relatively uncommon in developing nations, like China, five years ago. He attributed the rise in breast cancer rates to an increase in Western lifestyles. For example, a later childbearing age has been directly linked to an increased risk for breast cancer. As emerging nations become more developed, women tend to become pregnant at a later age, like their Western counterparts. It is trends like these that Kensler directly attributes to more than a twofold increase in breast cancer over the past 30 years in some areas of Southeast Asia. Poor diets (such as an increase in red meat), alcohol and tobacco are other factors that increase the risk of breast cancer and can, in some ways, be attributed to the Westernization of these countries. To help solve these problems, Kensler advocates similar recommendations to those given to American women: regular exercise, maintain a normal body weight, no tobacco use and decreased alcohol consumption.
Throughout the lecture Kensler emphasized what he believes to be a disconnect between science and public policy. He recognized that scientists have the tools to identify problems and develop solutions, but the delivery of these treatments often lacks government support. Nearly all the risk factors for cancer presented by Kensler were shown to have efficient, cost-effective solutions. Yet, he recognized the major constraints to implementation were a lack of government interest or funding, an insufficient local infrastructure and a lack of education about these risk factors. He ended his speech by acknowledging the role Hamilton students, with a liberal arts education, can play solving this global health crisis by combining public health issues with other disciplines to make these problems the focus of governments around the world.
-- by Ryan Seewald '10
Kensler began by describing the magnitude of the worldwide cancer problem as well as the causes and biology of the disease. Cancer currently accounts for 13 percent of deaths worldwide, or about seven million people annually. By 2030, this figure may rise to 20 million deaths annually. Of these deaths, the majority currently and will continue to occur in developing nations. Most affected will be Africa, Southeast Asia and parts of South America. By 2050, two-thirds of all cancers will occur in Southeast Asia, partially as a result of population growth in these areas. Cancer tends to have a late-life onset, occurring most frequently in persons over the age of 45. It can take three to four decades for this cancer to grow from a single cell to billions of cells in the body. Kensler sees this relatively slow growth rate as an opportunity for interference before the cancer spreads. Still, he says the most effective way to eliminate the growing cancer threat is prevention before the cells have a chance to form. He cited lung, liver and breast cancers to discuss the upward trend of cancer prevalence in the developing world and also offered some possible solutions to these growing afflictions.
Kensler identified three main causes of cancer. Tobacco use ties directly to the cause of about one-third of cancer, poor dietary habits accounts for another third, and infectious diseases directly contribute to about 20 percent. Of these, he emphasized tobacco as one of the greatest contributors to risk factors that could and should be decreased. Tobacco probably contributes to about 87 percent of the incidence of lung cancer. Not only do its carcinogens increase the risk for lung cancer, but it increases the risks for most other forms of cancer as well, including oral and esophageal. He pointed out that quitting smoking can decrease the risk of cancer by half in five years.
However, in countries such as China, which currently accounts for 33 percent of all tobacco use and where tobacco production is the country's largest industry, few steps have been taken to decrease the tobacco consumption throughout the country. Kensler found that in some rural areas, up to 50 percent of the annual income was spent on cigarettes. With such a high prevalence and a general lack of public knowledge about the potential side effects of smoking, China has a rapidly growing lung cancer incidence that will only worsen as the cancer develops in the current generations over the next several decades.
The incidence of lung cancer is further affected by the outdoor pollution associated with rapid urbanization of the developing world. Also, indoor use of biofuels, such as cow dung, in these developing nations further increases the amount of inhaled carcinogens. While Kensler pointed out that this last contributor is difficult to control on a large scale, he said that tobacco consumption and outdoor pollution should both be handled as matters of public policy. He emphasized the role of governments and world health organizations in spreading the message to control these factors.
Kensler also connected infectious agents to the high incidence of liver cancer in China and throughout the world. Infectious agents account for about 26 percent of all cancers in the developing world and only about eight percent in the developed world. Specific to Kensler's research, he and his American and Chinese colleagues found that exposure to the hepatitis B virus and aflatoxin, a dietary toxin from mold, increased the risk of liver cancer 60 times. Exclusive exposure to either of these diseases only slightly increased the incidence of cancer. Kensler recognized that by at least preventing one of these infectious agents from affecting the body, the incidence of liver cancer could be greatly reduced.
Currently in Africa and Southeast Asia less than 10 percent of all inhabitants are immunized against hepatitis B. Kensler identified economic constraints (the HBV vaccine is relatively expensive) as well as a lack of healthcare infrastructure in these developing nations as the principal cause of the lack of immunizations. As a result, Kensler sought a cost-effective and efficient method to help prevent the carcinogens in aflatoxin from settling in the body, as proper harvesting and food storage methods that prevent the mold from growing seemed difficult to teach on a large scale.
He and his colleagues found that certain vegetables, such as Brussels sprouts and broccoli, had an anticarcinogenic effect and that the active agent also dissolved well in water. They harvested these plants, heated them into tea, and found that they successfully decreased the effect of carcinogens on the body. Kensler believes these anticarcinogenics may offer one solution to the growing liver cancer epidemic, as the treatment is relatively easy to procure and administer. However, Kensler also recognizes that using Brussels sprouts in tea may not work as well in other areas, like Africa, where they are not used as commonly as in Southeast Asia.
Finally, Kensler discussed the growing incidence of breast cancer, both globally and in China. He described breast cancer as a primarily Western form of cancer that was relatively uncommon in developing nations, like China, five years ago. He attributed the rise in breast cancer rates to an increase in Western lifestyles. For example, a later childbearing age has been directly linked to an increased risk for breast cancer. As emerging nations become more developed, women tend to become pregnant at a later age, like their Western counterparts. It is trends like these that Kensler directly attributes to more than a twofold increase in breast cancer over the past 30 years in some areas of Southeast Asia. Poor diets (such as an increase in red meat), alcohol and tobacco are other factors that increase the risk of breast cancer and can, in some ways, be attributed to the Westernization of these countries. To help solve these problems, Kensler advocates similar recommendations to those given to American women: regular exercise, maintain a normal body weight, no tobacco use and decreased alcohol consumption.
Throughout the lecture Kensler emphasized what he believes to be a disconnect between science and public policy. He recognized that scientists have the tools to identify problems and develop solutions, but the delivery of these treatments often lacks government support. Nearly all the risk factors for cancer presented by Kensler were shown to have efficient, cost-effective solutions. Yet, he recognized the major constraints to implementation were a lack of government interest or funding, an insufficient local infrastructure and a lack of education about these risk factors. He ended his speech by acknowledging the role Hamilton students, with a liberal arts education, can play solving this global health crisis by combining public health issues with other disciplines to make these problems the focus of governments around the world.
-- by Ryan Seewald '10
