A 2004 study detected parabens in 18 of 20 samples of tissue from breast tumour biopsies. The study did not prove parabens cause cancer, only that they were easily detected among cancerous cells. Nevertheless, the results point to further investigation. For more than 25 years it has been know that estrogen exposure is linked to breast cancer development and progression. As parabens weakly mimic estrogen, there is concern that repeated, cumulative, long-term exposure to such chemicals may have an impact. Another study showed that parabens could be detected in the blood and urine of healthy young male volunteers a few hours after paraben-containing lotions were applied to their skin. The authors concluded that since the chemicals could be absorbed, metabolized and excreted, they could potentially contribute to adverse health effects. Though there is no conclusive scientific evidence that parabens are harmful to the body, some researchers feel there may be reason for concern.