Air pollution may be increasing breast cancer rates in the US, government research suggests.
Scientists found that areas where air toxic levels are highest are also home to some of the highest rates of the disease in women.
The study, conducted by the National Institutes of Health (NIH), is one of the largest of its kind, tracking the health records of nearly 200,000 women over two decades. It used a national health study and historical air quality estimates to determine whether there was an association between air pollution and breast cancer.
It found that every 10 micrograms per cubic meter (μg/m3) increase in levels of small particulate pollutants known as PM2.5 was associated with an eight percent increase in breast cancers.
PM2.5 is formed as a result of burning diesel, wood and coal and is so small that it can enter the bloodstream when inhaled, from where it travels to organs and causes damage linked to cancer and dementia.
In the photo above, heavy traffic on the Golden Gate Bridge in San Francisco. Among the places analyzed by the researchers, the majority of women diagnosed with breast cancer lived in California, 32 percent.
Shown above is a power plant in Louisiana. For the study, the team calculated estimated hazard ratios (HRs) for pollution exposure and breast cancer development. A risk index can be considered an estimate of risk, such as the risk of developing a disease in relation to exposure. Human resources were the lowest in Louisiana
The United States has considered PM2.5 levels between 12 μg/m3 and 15 μg/m3 as standard
Levels above 35 μg/m3 are considered harmful to health and prolonged exposure to levels above 50 μg/m3 can lead to serious health problems and premature death. Nationally, average PM2.5 concentrations have been declining for years.
PM2.5 has been inconsistently associated with breast cancer incidence; However, few studies have considered historical exposure, when contaminant levels were higher. While this study found an association between the two, scientists stressed that more research needs to be done on the topic at the national level.
Scientists at the National Institute of Environmental Health Sciences (NIEHS) and the National Cancer Institute (NCI), both part of the NIH, followed 196,905 women who had enrolled in the NIH-AARP Diet and Health Study between 1995. and 1996.
Most of the women in the study were over age 50, and the researchers’ analysis consisted primarily of postmenopausal women, a limitation of the study, the researchers noted.
The study included women from California, Florida, Louisiana, New Jersey, North Carolina, Pennsylvania, Atlanta and Detroit.
Analyzing follow-up data through 2017, researchers identified 15,870 cases of breast cancer and found that a 10 μg/m3 increase in PM2.5 between 1980 and 1984 was associated with an eight percent increase in the overall risk of breast cancer. breast cancer.
The graph above shows the rate of breast cancer cases among women as a rate per 100,000 people compared to the death rate shown in the red squares. While case rates continue to rise, deaths have decreased. The blue and green dots come from two different databases that track breast cancer rates over different time periods.
Dr Alexandra White, lead author and head of the NIEHS Environment and Cancer Epidemiology Group, said: “We saw an eight per cent increase in breast cancer incidence in people living in areas with higher PM2 exposure. ,5.
“Although this is a relatively modest increase, these findings are significant given that air pollution is a ubiquitous exposure that affects almost everyone.
“These findings add to a growing body of literature suggesting that air pollution is linked to breast cancer.”
Among the places analyzed in the study, the researchers found that the majority of women diagnosed with breast cancer lived in California, 32 percent, and Florida, 21 percent.
Specifically, the association was found for ER+ tumors, masses that are estrogen receptor positive, allowing the tumor to use estrogen to grow. The association was not found for estrogen receptor-negative tumors.
ER+ tumors grow more slowly and patients with this type of breast cancer tend to have better short-term outlook, although the cancer can return many years after treatment.
The associations were similar in the other periods the researchers examined: 1985 to 1989 and 1990 to 1994.
PM2.5 is classified as a human carcinogen and contains nickel, sodium, silicon, ammonium, nitrate and sulfate, among others. Many of these can disrupt the endocrine system, which controls the body’s hormones.
For the study, the team calculated estimated hazard ratios (HRs) for pollution exposure and breast cancer development.
A risk index can be considered an estimate of risk, such as the risk of developing a disease in relation to exposure. The researchers determined that a 10 μg/m3 increase in PM2.5 was associated with breast cancer incidence with an HR of 1.08.
When an HR is positive, it means that there is a higher risk of contracting the disease among exposed people compared to the unexposed group.
HRs were highest in North Carolina and Atlanta, meaning women exposed to PM2.5 there had a higher risk of developing breast cancer. HRs were lower in Louisiana and California, although they were still positive.
