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Bladder cancer

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Risk factors for bladder cancer

A risk factor is something that increases the risk of developing cancer. It could be a behaviour, substance or condition. Most cancers are the result of many risk factors. Smoking is the most important risk factor for bladder cancer.

The risk of developing bladder cancer increases with age. It usually occurs in people older than 65 years of age. Bladder cancer is most common in Caucasians, and men develop this disease more often than women.

Risk factors are generally listed in order from most to least important. But in most cases, it is impossible to rank them with absolute certainty.

Researchers have looked into alcohol, artificial sweeteners, coffee and tea. They have found that there is no link between these factors and a higher risk for bladder cancer.

Known risk factors

There is convincing evidence that the following factors increase your risk for bladder cancer.

Smoking

Most bladder cancers are linked to smoking tobacco. It is most strongly associated with smoking cigarettes, but smoking cigars and pipes also increases the risk for bladder cancer.

The risk for bladder cancer is linked with the amount you smoke per day, the number of years you have smoked and how old you were when you started smoking. Smokers and former smokers are much more likely to develop bladder cancer than people who have never smoked.

Arsenic

Arsenic is a substance found in nature. Sometimes drinking water can be contaminated with high levels of arsenic, which increases the risk for bladder cancer. The arsenic can come from natural sources, such as rocks and soil. It can also come from certain types of mining, smelting or manufacturing plants.

Occupational exposure to chemicals

Workers in the following industries have a higher risk of developing bladder cancer:

  • professional painting
  • rubber manufacturing
  • aluminum and metal production
  • textile and dye manufacturing
  • transportation

This higher risk is linked to exposure to certain chemicals. Your risk is especially high if you are exposed to aromatic amines, including 2-naphythylamine, benzidine, 4-aminobiphenyl and o-toluidine. Exposure to polyaromatic hydrocarbons (PAHs), 2-mercaptobenzothiazole and magenta production also increases the risk for bladder cancer.

Exhaust from diesel engines has also been identified as a likely cause of bladder cancer, but the link isn’t as strong as it is for the chemicals listed above.

Smokers who are exposed to these chemicals in the workplace have an even higher risk of developing bladder cancer.

Cyclophosphamide

People who have been treated with the chemotherapy drug cyclophosphamide (Cytoxan, Procytox) have a higher risk for bladder irritation, which in turn increases the risk of developing bladder cancer.

To help protect the bladder, it is important to drink plenty of fluids during treatment with cyclophosphamide. Sometimes doctors will give other drugs to help protect the bladder from irritation.

Exposure to radiation

People who received radiation therapy to the abdomen or pelvis have a higher risk for bladder cancer. People who are exposed to radiation at work or who have survived atomic bombs or nuclear accidents also have a higher risk for bladder cancer.

Chronic bladder irritation

If you often have bladder irritation, or if bladder irritation lasts a long time, you have a higher risk for bladder cancer. Inflammation or injury can cause chronic bladder irritation.

Inflammation can be caused by bladder stones or chronic bladder infections. Schistosoma haematobium (S. haematobium) is a parasitic worm that infects the bladder and causes inflammation (called schistosomiasis or bilharziasis). This type of bladder infection occurs most often in developing countries. Chronic infection with S. haematobium increases the risk for bladder cancer.

The bladder can be injured by having a catheter in for a long time, which some people need to help them empty their bladders.

Personal history of cancer in the urinary tract

Having a cancer in any part of the urinary tract increases the risk of developing another tumour in the urinary tract, including in the bladder.

Bladder birth defects

Urachus and exstrophy are rare birth defects that increase a person’s risk of developing bladder cancer.

The urachus is the connection between the navel, or belly button, and the bladder. It develops in a fetus and remains as a thin strip of fibrous tissue in an adult. The urachus can become cancerous if a cyst forms along it or if it remains partly open.

Exstrophy is when skin, muscle and connective tissue in front of the bladder do not close completely during development and leave a hole in the wall of the bladder. The inside of the bladder can be exposed to micro-organisms. This exposure can lead to chronic infections, which increase the risk for bladder cancer. Doctors treat exstrophy as soon as it is found, but people with this birth defect have a higher risk of developing bladder cancer throughout their lives.

Possible risk factors

The following factors have been linked with bladder cancer, but there is not enough evidence to show they are known risk factors. More research is needed to clarify the role of these factors for bladder cancer.

Aristolochic acids

Studies show that aristolochic acids are present in some types of plants. They may increase the risk of developing urothelial carcinoma in the ureters and the renal pelvis in the kidney. People may be exposed to aristolochic acids if they eat or drink herbal products (including capsules, extracts, teas and dried herbs) that contain the plant species Aristolochia.

Chlorine by-products

People who for most of their lives drink water from a river, lake or reservoir that is treated with chlorine may have a slightly higher risk for bladder cancer. When chlorine is used to disinfect water and make it safe for drinking, it breaks down into different chemicals called chlorine by-products. The chlorine by-products that may increase the risk of bladder cancer are called trihalomethanes (THMs). Research is looking at other chlorine by-products that may also increase risk.

Working as a hairdresser

Studies suggest that hairdressers may have a higher risk for bladder cancer. Researchers think that this risk is connected to exposure to hair dye. The evidence for this increased risk comes mainly from studies looking at hairdressers before 1980. After that year, the chemicals that may cause cancer were banned from professional hair dyes.

Family history

A family history of bladder cancer may increase the risk of developing this type of cancer. Researchers don’t know if certain genes or other factors that are passed from parents to children make families more likely to develop bladder cancer when exposed to bladder cancer risk factors.

Outdoor air pollution

Several studies show that outdoor air pollution may increase the risk for bladder cancer. Chemicals in the air that may increase the risk include arsenic and aromatic amines.

Pesticides

Some studies of farmers show that these pesticides may increase the risk for bladder cancer:

  • chlorophenoxy
  • organochlorine pesticides
  • imazethapyr
  • imazaquin

Certain medicines

Phenacetin is a drug used to relieve pain. When it is taken in large doses over a period of time, it can cause cancer of the ureters and the renal pelvis in the kidney. As a result, it has not been available in Canada since 1973. A number of studies show that heavy use of phenacetin is linked to a higher risk for bladder cancer, but others found the risk was only for ureter and renal pelvis cancers.

Pioglitazone is a medicine used to treat diabetes. Studies show that it may increase the risk for bladder cancer, especially in people who take it at higher doses for long periods of time.

Unknown risk factors

It isn’t known whether or not the following factors are linked with bladder cancer. It may be that researchers can’t show a definite link or that studies have had different results. More research is needed to see if the following are risk factors for bladder cancer:

  • not drinking enough fluids
  • dying your hair
  • smoking opium

Questions to ask your healthcare team

To make the decisions that are right for you, ask your healthcare team questions about risks.

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