Cancer is the No. 2 cause of death in the US, second only to heart disease.
It fundamentally affects the way our cells grow and divide, changing them in perverse ways. All cancer is a result of damage or genetic mutations in our DNA. The nasty, debilitating class of diseases spreads through a body like an invading army, as toxic cells grow relentlessly into unruly tumors.
Some cases of cancer are out of our control, determined by genetic defects and predispositions passed down from one generation to the next, or spurred by genetic changes we undergo through our lifetime.
But we also know that breathing in certain substances, eating specific things, and even using some kinds of plastics ups the risk of developing some deadly cancers.
Here are some known carcinogens (cancer-causers), as well as a few more things scientists are zeroing in on as prime suspects.
Scientists now know that eating too much sweet stuff can not only lead to diabetes, but actively damage your cells and increase your risk of developing cancer.
But that's not all.
New research suggests that sugar may fuel tumor growth in the body — because cancer loves to use sugar as fuel.
"The hyperactive sugar consumption of cancerous cells leads to a vicious cycle of continued stimulation of cancer development and growth" Johan Thevelein, a Belgian molecular biologist, said in October after the release of his study.
Scientists say that the groundbreaking research gives us a better understanding of how sugar and cancer interact and that it could one day help create targeted diet strategies for patients.
Any food that comes in a crinkly plastic wrapper, is industrially sealed, and is designed to last for months without spoiling may be a quick on-the-go fix for a hunger pang, but it's also most likely increasing your risk of cancer.
Scientists in France recently zeroed in on a link between people who eat more processed foods and those who develop cancer.
They're not sure yet whether the problem is the shelf-stabilizing ingredients, the plastic packaging, or some combination of the two. And because their study was correlative, it's possible there's some other hidden factor at work.
Though the tobacco industry tried to cover this one up, we've known for years that tobacco smoke has at least 70 cancer-causing chemicals inside.
And it's not just smokers who are affected — people who inhale secondhand smoke can develop deadly forms of cancer too.
The Centers for Disease Control and Prevention says: "Nonsmokers who are exposed to secondhand smoke at home or at work increase their risk of developing lung cancer by 20-30%."
People who chew their tobacco are at increased risk too.
Tanning and unprotected sun exposure
According to the Skin Cancer Foundation, people who use a tanning bed before age 35 increase their risk of developing melanoma by 75%.
Regular sun can hurt you too, so wearing protective clothing and sunscreen and finding shade are good ideas if you're going to be out in the sunshine for more than 15 minutes.
Toxic chemicals at work
Some people work with cancer-causing substances daily.
Those at risk of coming in contact with cancer-causing substances on the job include:
• Aluminum workers.
• Tar pavers, who come in contact with the carcinogen benzene.
• Rubber manufacturers.
• Hairdressers who deal with dyes every day.
• Nail-salon workers breathing in dangerous fumes.
• And everyone who works the night shift (the International Agency for Research on Cancer classified nighttime work as a probable carcinogen in 2007).
The CDC has a full list of occupational cancer hazards.
Arsenic, a natural part of the Earth's crust, is toxic in its inorganic form. It's often found in contaminated drinking water in places like Bangladesh, or in spots where irrigation systems for crops use arsenic water.
The World Health Organization says at least 140 million people in 50 countries drink water containing high levels of arsenic.
It's also one of the cancer-causing agents in tobacco.
Charred meat, and grilling over an open flame
Smoky meats from the grill may be tender and tasty, but they probably also increase your risk of cancer. That's because the muscle meats contain compounds called heterocyclic amines, or HCAs, and polycyclic aromatic hydrocarbons, or PAHs.
According to the National Cancer Institute, when meats like beef, poultry, or fish are cooked over a hot open flame or pan-fried at high temperatures, the fat and juices they release into the fire spark flames with the dangerous chemicals inside that then cook into the meat we eat.
They're not positive that these chemicals cause cancer, but in lab tests they have been found to change DNA in ways that might increase the risk of cancer.
Coal miners have for years had higher rates of cancer in their lungs, bladder, and stomach. There's sufficient data to suggest miners who deal with coal gasification or who inhale coal dust can get cancer.
Regular heavy alcohol consumption can up your risk of developing several different kinds of cancer, including throat, liver, breast and colon cancer.
According to the National Cancer Institute, "the risk of developing cancer increases with the amount of alcohol a person drinks."
Diesel oil has more than 30 components that can cause cancer, according to the International Agency for Research on Cancer.
Salt-cured meat or fish and pickled foods
Salt-cured fish, which is popular in China, is high in nitrates and nitrites — known carcinogens in animals that may also cause cancer in humans. The chemical compounds can damage DNA, leading to head and neck cancer.
According to Cancer Research UK, "people from China, or with Chinese ancestry living in the UK, have higher rates of nasopharyngeal cancer than other ethnic groups," something that might be because of their diet.
Eating lots of pickled foods can also increase your risk of stomach cancer.
Chemicals used in oil fracking that may be released into air and water include the cancer-causers benzene and formaldehyde.
Processed meats like ham, bacon, and sausage
The World Health Organization says processed meats like hot dogs, ham, bacon, and sausage can cause cancer. That's because the meat has been treated in some way to preserve or flavor it, such as by salting, curing, fermenting, or smoking.
The WHO also says it's possible that any kind of red meat could be linked to an increased risk of cancers like colorectal cancer.
Asbestos was used as an insulation material for years before the dust was linked to lung cancer.
Products that contain asbestos are not completely banned in the US, though the Environmental Protection Agency regulates their use.
Birth control and estrogens
Hormones can cause cancer too.
Women who start menstruation early or go into menopause later can increase their risk of breast cancer because they're exposed to more estrogen and progesterone made by the ovaries.
Using birth control pills can also increase a woman's risk of developing breast and cervical cancers.
Catching certain kinds of viruses can indirectly increase your risk of cancer. That's because in some situations, viruses trigger genetic changes in cells that can contribute to cancer.
The CDC says: "Some viruses linked to cancer are the human papillomavirus (HPV), which causes cervical cancer; hepatitis B and C viruses, which can cause liver cancer; and the Epstein-Barr virus, which may cause a type of lymphoma. Also, the H. pylori bacterium can cause gastric cancer."
Some cancer risk is passed down from one generation to the next. Genetic mutations play a key role in about 5-10% of all cancers.
"Genetic changes that promote cancer can be inherited from our parents if the changes are present in germ cells, which are the reproductive cells of the body (eggs and sperm)," the National Cancer Institute says.
For example, certain kinds of breast cancer are a result of mutations in the BRCA1 and BRCA2 genes.
Obesity can put you at increased risk of developing types of cancers including breast, colon, rectum, esophagus, kidney, and pancreas.
Prevention includes eating healthy foods and getting enough physical activity, both of which not only help people maintain a healthy weight, but also reduce the risk of some of those cancers.
Scientists have known for years that formaldehyde can cause nasal cancer in rats.
The preserving agent and disinfectant is used in some glues and building products, and the International Agency for Research on Cancer says it can cause cancer in humans too.
Smoggy air — and the particulates in it — can also lead to cancer.
Soot in general isn't great. In London, people started noticing lots of chimney sweeps developing scrotal cancer in the 1770s, and further studies found a link between the backbreaking chimney work and higher cancer rates.
Soot inhalation has also been linked to lung, esophageal, and bladder cancers.
Silica is a natural mineral found in sand, stone, and concrete. But when construction workers and miners inhale silica particles by cutting, sawing or drilling into rock, it can increase their risk of developing lung cancer.
We know that X-rays and gamma rays can cause cancer. We can also get it from solar UV rays.
But one trip to the doctor isn't going to give you cancer.
The link between radiation and cancer risk tends to show up in studies of people who've been exposed to high doses of radiation, like people affected by the Chernobyl nuclear accident, and people who have cancer, who are sometimes treated with high doses of radiation.
Still, the American Cancer Society cautions that "there is no threshold below which this kind of radiation is thought to be totally safe."
Chronic, long-term, DNA-damaging inflammation
Chronic inflammation from things like long-term infections, bowel disease, or obesity can all damage a person's DNA and lead to higher cancer rates.
Plastics can be dangerous, especially when they leach chemicals out through scratches or cracks in a container.
BPA is a synthetic estrogen that has been used in many plastics and resins since the 1960s. BPA resins can be used inside products like metal food cans as sealants, while polycarbonate BPA plastics can include water bottles and food storage containers.
BPA even shows up on the shiny side of receipt paper to stabilize the ink.
While many plastics manufacturers have started labeling their products "BPA-free," there's still a lot of the breast- and prostate-cancer-causing stuff around.
The browning of some foods cooked at high temperatures — like bread, coffee, or biscuits — produces a chemical compound called acrylamide.
This happens naturally in a process called the Maillard reaction.
But the dose of acrylamide in a toasty cup of coffee or a chewy cookie is probably not going to kill you — it's dangerous when consumed in large doses (and it's one of the toxic chemicals smokers inhale), but there's no evidence that a little browning is harmful.
A California judged ruled this week that some companies that sell coffee sellers must include labels warning their customers about the possible cancer risks.
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