How air pollution causes girls to reach puberty earlier

Piece by: BBC

• This trend is not limited to the US; it's happening globally. South Korean scientists have noted that girls are developing breasts and starting their periods earlier.

A girl staring out a window
Image: Lucija Rasonja from Pixabay

A new study reveals that girls in the United States are reaching puberty earlier, with toxic air being a significant factor.

Historical Context

For decades, scientists worldwide have been concerned about girls entering puberty at younger ages compared to previous generations.

  • Past vs. Present: Girls in the US are now estimated to start their periods four years earlier than girls who lived a century ago.
  • Research Data: A report from May shows that girls born between 1950 and 1969 began menstruating at an average age of 12.5 years. By the early 2000s, the average age dropped to 11.9 years.

Global Trends

This trend is not limited to the US; it's happening globally. South Korean scientists have noted that girls are developing breasts and starting their periods earlier.

  • Economic and Social Factors: Audrey Gaskins, a professor at Emory University, points out that this decrease in puberty age is more prevalent in economically disadvantaged communities and among minority groups.

Health Implications for Girls

Gaskins highlights that early puberty can lead to a range of health issues later in life.

  • Health Risks: Early menstruation is linked to reduced fertility, earlier onset of menopause, and a shorter lifespan. It also increases the risk of breast and ovarian cancer, obesity, type 2 diabetes, and cardiovascular diseases.
  • Behavioral Concerns: Brenda Eskenazi, a public health professor at UC Berkeley, notes that girls who mature early are more likely to engage in sexual activity sooner, leading to higher rates of teenage pregnancies.

Causes: Obesity and Air Pollution

For years, scientists believed childhood obesity was the primary cause of early puberty, with proteins produced by fat cells being a major factor.

  • Recent Studies: In the past three years, research has identified another surprising cause: air pollution.
  • Specific Pollutants: Studies, including one from Ewha Womans University in Seoul, link pollutants like sulfur dioxide, nitrogen dioxide, carbon monoxide, and ozone to early puberty. These pollutants often come from vehicle emissions and industrial smoke.

Case Study: Poland

In 2022, Polish scientists studied 1,257 women in a region known for industrial air pollution. They found a connection between nitrogen gas exposure and menstruation before age 11.

Biological Mechanism

Gaskins explains that inhaling toxic air allows pollutants to enter the lungs and reach various organs, including the placenta, fetal tissues, and ovaries.

  • Hormonal Disruption: Airborne chemicals can interfere with hormones like androgens and estrogens, potentially triggering early puberty.

Other Contributing Factors

While air pollution is a significant factor, other elements may also contribute to early puberty.

  • Cosmetic Products: Gaskins mentions that personal care products containing harmful chemicals can disrupt hormonal processes.
  • Environmental and Psychological Influences: Eskenazi suggests that many factors, including climate change and social stressors, might impact child development.


Girls reaching puberty earlier is a documented reality with likely multifaceted causes, including environmental chemicals, obesity, and psychological factors. More research is needed to fully understand these dynamics and their long-term implications.

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