When Ida Washington received a letter inviting her to participate in a women’s health study to explore the environmental roots of breast cancer, she didn’t think twice. Her mother was diagnosed with the disease nearly 40 years ago, and since then, it has been a terrifying mystery she has yearned to unravel.

Washington was just a teenager when the lump was found on her mother’s left breast. In the years that followed, as her mother’s cancer went into remission, she began to wonder what caused it. “My mother didn’t smoke, she didn’t drink. Breast cancer didn’t run in the family,” she said.

Ida’s mother, Willie Mae Washington, now 92, participated in the first generation of a scientific study that has endured for more than half a century to investigate whether environmental exposures may trigger breast cancer. Now Ida Washington, 52, is continuing the legacy as part of its second generation.

The two women are among the more than 15,000 mothers, daughters and granddaughters in the San Francisco Bay Area enrolled in a project known as the Child Health and Development Studies, launched in 1959. Tens of thousands of samples of the women’s blood are stored, providing more than 50 years of continuous data on health outcomes and environmental exposures.

Scientists tap into this unique trove as they struggle to figure out what role environmental exposures play in the development of diseases such as breast cancer.

“These women are a national treasure,” said Barbara Cohn, director of the Child Health and Development Studies and Three Generations follow-up study, based in Berkeley, Calif. “They hold the key to understanding the risks.”

While billions of research dollars have been spent on screening, treating and trying to cure breast cancer, still relatively little is known about its causes. One in every eight women today will contract the disease during her lifetime. Genes account for only a small number of cases, 5 to 10 percent. Known risk factors include age, obesity and low physical activity.

Washington, her mother, and other members of the Bay Area study are uniquely poised to help researchers answer the why’s of breast cancer and other diseases afflicting women.

Over the years, this group of women and their children – known in scientific jargon as a cohort – has helped scientists understand how diseases can start even before birth and may pass from one generation to the next – not just through genes, but also by things in their environment.

Funded largely by the National Institutes of Health, hundreds of scientific studies have been published about these women since the 1960s.

One of the more groundbreaking findings provided a clue that smoking during pregnancy could harm the fetus. Also, based on these women, scientists discovered that exposure to the now-banned pesticide DDT during a mother’s pregnancy could decrease a daughter’s ability to become pregnant and increase a son’s risk of testicular cancer. New findings are expected to be published soon.

There are no research cohorts like it in the country. In fact, it may be the only one of its kind in the entire world.

The study group is “extremely valuable, almost unique,” said Shanna Swan, an environmental health scientist at Mount Sinai School of Medicine in New York who is not involved with the California research.

Because of its size and longevity, the Child Health and Development Studies is helping researchers tease apart the complex series of events and exposures starting before birth that may lead to cancer and other diseases many decades later. A growing number of studies suggests that the hormones and chemicals a child is exposed to in the womb may play a big role in her development of a number of diseases.

The decades-old blood is what makes the research so exciting, said Julia Brody, executive director of the Silent Spring Institute, a non-profit breast cancer research organization based in Massachusetts.

“It’s so helpful to have both measurements collected years ago and the potential to follow people for a long time to see what happens,” said Brody, who is an advisor for the Three Generations Study.

In the 1950s, scientists were not thinking about the fetal origins of adult diseases. They were not archiving blood and urine from pregnant women and their newborns for future generations of researchers to study. That all changed with the forward-thinking scientists in Oakland.

In 1959, under the direction of Jacob Yerushalmy, a professor of biostatistics at the University of California, Berkeley, the first participants were enrolled through their health insurance provider, Kaiser Permanente. Over the years, many study families stuck with Kaiser. Having all study participants initially on a single health plan with its own clinics and hospitals helped researchers gather detailed information and samples from the families.

At doctor’s visits during childhood and adolescence, Ida Washington, who lives in San Leandro, Calif., remembers filling out questionnaires and having body measurements taken. “I never thought much about it,” she said. “The tests were just part of the routine.” It wasn’t until several years later, when she received that letter in the mail, that she realized what it was all for.

Ida works as a claims assistant for Kaiser Permanente in Oakland. She has a 30-year-old son she hopes will be asked to participate in a men’s follow-up study. Her mother, Willie Mae, who worked as a nursing aid in convalescent and private homes at the time, no longer remembers when she was approached about the study or why she joined. “I think shortly after Ida was born,” she said. “I had three older children. Ida was my baby.”

The blood that Ida’s mother and the others provided years ago was frozen and now resides at a storage facility in Reston, Va. Cohn, the study director, rations serum from the archived vials sparingly. When the vials are gone, so is the information – and potential – that they hold.

New blood and urine samples, provided by the second generation of women, now in their late 40s and early 50s, as well as their daughters, are processed and stored at a state-of-the-art biorepository on the University of California, Berkeley's new Bay campus.

Decades ago, blood was simply put in a vial and frozen. Now scientists have come up with more sophisticated methods of dividing and preserving samples to ensure that researchers can extract even more data, explained Nina Holland, a professor at the School of Public Health and director of the biorepository where the new vials are kept.

Holland’s biorepository catalogues and stores specimens from 32 completed and ongoing scientific studies, but few of them contain the depth of information as the Child Health and Development Studies.

“The fact that you can go back 50 years is remarkable. This is probably one of the most valuable studies,” she said. It not only traces the health of its women over generations, but also allows researchers to go back and make connections between exposures they had early in life and diseases they developed as adults.

Like Ida Washington, study participant Laurie Havas, also 52, had no idea as a child that she was part of a multigenerational research project that her mother had joined before her birth. Laurie’s mother died of pancreatic cancer when Laurie was 21. Laurie does not know why her mother joined the study, but when she got a letter in the mail some years later, asking her to participate in a follow-up, she knew it was something she had to do.

“I am doing it for myself and my mother. I am continuing her legacy. It makes me feel closer to her,” she said.

Havas, who lives in Pleasant Hill, Calif., has two children, a 17-year-old son and a 20-year-old daughter. Her daughter has so far declined to participate as an adult in the study, but Havas hopes that some day she will change her mind.

Both Havas and Ida Washington feel that they are part of something bigger than themselves: They are partners in a quest to find answers for the causes of breast cancer and other diseases. Cohn is trying to ensure the project's funding, reliant on federal grants, continues long into the future, although nothing is guaranteed.

Like most people, Ida Washington hopes one day for a cure for breast cancer. And while she realizes she may never know why her mother developed the disease nearly 40 years ago, she understands that the cure and the cause are inextricably linked. “How can we begin to find a cure if we don’t first know the cause?” she asked.

Nobody knows exactly how many years, months and days it will take to answer those questions, or if those answers will ever be available to help any of the women now in the study who may develop breast cancer in their lifetime.

But the legacy of these women will live on, with their blood and tissue samples providing clues that will endure long after they die.

Havas, for one, has her sights trained on the future. “The things going into my body when I was pregnant with my daughter, the things going into my daughter’s body, the more we can grasp, the more we can affect the future.”

“The future,” she said, “is now.”

Read Part 1

This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.