Why are girls starting puberty earlier?

“We are also seeing that these decreasing ages at puberty are even more pronounced in lower socioeconomic status groups, and in minority ethnic groups,” he says. Audrey Gaskins, associate professor at Emory University in Atlanta (USA). “This has important long-term health implications.”

Researchers like Gaskins are primarily concerned that the early onset of puberty could trigger a cascade of events with far-reaching consequences in adulthood.

New data suggests that it may not only shorten the window of fertility, especially if these women enter menopause earlier, but also shorten their lives.

Precocious puberty has repeatedly been associated with an increased risk of diseases ranging from breast and ovarian cancers, metabolic syndromes such as obesity and type 2 diabetes, and cardiovascular diseases.

Scientists are still trying to understand why this happens, but Brenda Eskenazia professor of public health at the University of California, Berkeley, says one theory suggests that if the body’s cells are exposed to circulating levels of sex hormones like estrogen over a longer period of time, this may increase the risk of developing of tumors because these hormones stimulate cell growth.

“There are some theories that having a longer window of exposure to hormones increases the risk of reproductive cancers,” he says.

But why does child development accelerate like this?

The onset of puberty is dictated by two powerful communication networks in the body known as the hypothalamic-pituitary-adrenal (HPA) and hypothalamic-pituitary-gonadal (HPG) axes.

These connect a region of the brain called hypothalamuswhich regulates various essential body functions, from hunger to temperature control, with different hormone-secreting glands.

Gaskins says that until 10 or 20 years ago, scientists assumed that the only cause of premature puberty was childhood obesity, and that proteins produced by fat cells, called adipokines, played a role in stimulating the HPA and HPA axes. HPG. “Only recently has it been said, ‘Oh, that doesn’t explain everything, and there must be other factors involved,'” he says.

Instead, several studies conducted in the last three years have pointed to another, more surprising cause: the atmospheric pollution.

Much of this research has been carried out by scientists from South Koreawhere Seoul, Busan and Incheon are among the 100 most polluted cities in the world.

A study recently published by Ewha Womans University in Seoul has detected a repeated relationship between exposure to various pollutants and earlier puberty.

Some of the main culprits appear to be toxic gases such as sulfur dioxide, nitrogen dioxide, carbon monoxide and ozone, all released into the air through vehicle emissions or waste produced by factories.

In 2022, a study conducted by scientists from Polanda country known for its poor air quality due to the prevalence of coal-burning factories, examined data from 1,257 women and found a relationship between increased exposure to nitrogen gases and the onset of menstruation before age 11.

Perhaps of even greater concern is the fine particulate matter (PM)particles that are too small to see, but are released into the air from sources ranging from construction sites to forest fires, power plants, vehicle engines and even dusty, unpaved roads.

In October 2023, Gaskins and her colleagues found that American girls exposed to high amounts of PM2.5 – defined as particles with a diameter less than 2.5 μm – and PM10, both in utero and during infancy, have more likely to have their first menstruation at a younger age.

“PM2.5 particles can enter the bloodstream quite easily,” says Gaskins.

“They are inhaled into the lungs and are not filtered like other larger particles, so they can reach different organs. We have seen that certain PM2.5 particles accumulate in the placenta, fetal tissues, ovaries, they can reach all parts”.

Studies carried out with mixtures of particles found in indoor air samples have shown that the chemicals contained in these fine particles are capable of interacting with the receptors of several hormones involved in development, in particular androgens and estrogens. This can cause a chain reaction that leads to the onset of puberty.

At the same time, there are likely many different factors involved in premature puberty.

Gaskins suggests that new tests related to PM2.5 and other pollutants are just one example of how Environmentally harmful chemicals can enter the body, stimulating powerful hormonal changes.

“Prepubertal girls are an interesting group because another important route of exposure to chemicals that disrupt hormonal processes is personal care products,” explains Gaskins. “And now there are a lot of companies that are actively going after that demographic and marketing products to them.”

Overall, Eskenazi says there is still much we don’t know about the complex connection between our changing world and how these fluctuations are impacting child development, with the role of factors such as microplastics and even climate change largely unknown.

“I think we’re still at the tip of the iceberg,” he says.

“We don’t know how a warmer climate affects the menstrual cycle, or even the role of social factors, which pressure girls to grow up earlier. But this trend is very real, and it could be a multifactorial combination of environmental chemicals , obesity and psychosocial problems that combine to reduce the age of menarche.