Why is breast cancer so much deadlier in black women than in white women? On the heels of an alarming new report that black women have caught up with their white counterparts in breast cancer rates, the question has taken on a fresh urgency.

But the answer is elusive.

The report, which the American Cancer Society released on Thursday, is a warning that breast cancer will cause an increasing loss of life for black women, who are already hit hardest by the disease. Black women are less likely to die of breast cancer today than they were 25 years ago. But a vast racial disparity in mortality rates has continued to widen: in 2012, black women were 42% more likely to die from breast cancer than white women.

Researchers have known for decades that breast cancer takes a deadlier toll on black women. “Hundreds of studies have looked at the differences in incidence and mortality rates between black women and white women,” said Linda Blount, CEO of the non-profit Black Women’s Health Imperative. “Hundreds. We can tell you it exists – the ‘what’. What we don’t know is the ‘why’.”

Thursday’s report points to several possible explanations for why the incidence of breast cancer is rising in black women. (In white women, the rate has remained flat for a decade.) Obesity is on the rise in black women, and black women are having fewer children, later in life. Susan Brown, who directs health education programs for the Susan G Komen breast cancer foundation, added that black women breastfeed at comparatively low rates. All are risk factors associated with breast cancer.

Other researchers have pointed to disparities in comprehensive access to competent medical care to explain both the incidence rate and mortality rate. A 2014 analysis of morbidity rates in the country’s 50 largest cities found that black women in Los Angeles were 70% more likely to die of breast cancer than white women. In New York, that number was 19%, leading researchers to believe that the city’s superior hospital and transportation system could be factors.

But these explanations do not fully satisfy a growing cadre of researchers calling for better investigation into breast cancer’s root causes.

“In general when we’re looking at breast cancers in all women, we tend to look at, what did they do wrong?” said Dr Mhel Kavanaugh-Lynch, director of the California Breast Cancer Research Program. “Did they eat wrong, exercise wrong, make their reproductive choices wrong, did they not get screened?”

Kavanaugh-Lynch thinks this is the wrong line of inquiry. While acknowledging that black women in America lack equal access to medical care, Kavanaugh-Lynch is troubled by studies in Canada and the UK finding that even black women who do get equal care at equivalent stages of the disease still die at lopsided rates.

Beginning in 2010, her group funded a multimillion-dollar investigation into the impact of factors commonly cited for those mortality rates: socioeconomic status, obesity, physical activity and other health conditions that coexist in black women with breast cancer.

Their results showed that controlling for these factors didn’t sufficiently explain the difference between outcomes for black and white women.

Instead, Kavanaugh-Lynch draws a potential connection between black mortality and incidence rates and the dearth of funding for environmental studies.

“Very little has been done to assess what is wrong with our social and physical environment that might be causing an epidemic in breast cancer,” Kavanaugh-Lynch said.

An expanding body of evidence suggests that certain chemical exposures in the womb may influence who develops breast cancer in adulthood. Traditional studies, which involve surveys or interviews of mostly older women who already have breast cancer, are poorly designed to capture those environmental factors.

“Environmental research could very well be a key,” to the racial disparities, Kavanaugh-Lynch said. “They’re related: difficult social conditions are often intermixed with chemical exposures.”

She noted that black women are more likely than white women to be diagnosed with a form of breast cancer, triple-negative, that resists treatment, and less likely to develop a form of breast cancer that is most responsive to therapies – and that years of traditional inquiries have failed to reveal why.

Karuna Jaggar, the executive director of Breast Cancer Action, an advocacy group that has been critical of mainstream breast cancer organizations, notes that such groups have been slow, in the past, to acknowledge those chemical and environmental factors.

In the wake of Thursday’s news, cancer organizations have reaffirmed their commitment to staunching the disease among black women.

“We are actively engaged in health equity efforts to really address these disparities,” says Brown, the Komen official. In addition to years of research into why breast cancer is so fatal to black women, she said, “We’re testing different patient navigation models for black women who have trouble accessing healthcare.”

But Thursday’s report also exposed a disconnect between leading cancer groups and black women who face the disease.

In a major announcement earlier this month, the American Cancer Society revised its guidelines for annual cancer screening, raising the suggested age for regular mammograms from 40 to 45. The move came after a sweeping review of academic research cast doubt on the link between early detection and saving lives. One influential study found that over 10 years, for every 10,000 women over 50 who has a regular mammogram, only 10 receive lifesaving care as a result. Another 6,130 women are given false positives and 940 women undergo unnecessary biopsies.

More breast cancer screenings, Kavanaugh-Lynch says, are not key to reducing black mortality rates. In California, she notes, black women have a higher screening rate and still die more often of breast cancer. But Blount noted that the revised guidelines at the very least send conflicting messages, as black women develop and die from breast cancer at younger ages than white women.

“For the average black woman out there who is trying to pay attention to the conversation about guidelines, we have completely confused her,” Blount says. “Mainstream feminist organizations have to think about these issues.” (Her group opposes the new guidelines.)

Jaggar, likewise, wishes that legacy groups would speak louder about the particular struggles facing black women with breast cancer. “Many organizations are just silent about the unacceptable disparities and inequities facing black women with breast cancer,” says Jaggar. “Where they do talk about it, they seem to be satisfied with describing it. The question is, for me, what are the actions that actually make the difference?”