Health officials announced Friday that they have discovered a small but "statistically significant" increase in the number of bladder cancers in North Portland between 1999 and 2003.
The Oregon Health Authority has been looking at cancer rates in neighborhoods around two glass manufacturers in Portland after a notable increase in air pollution was detected earlier this year.
The manufacturers had been using heavy metals like cadmium and arsenic to color glass, and elevated levels were found nearby.
Over a longer term, levels weren't as high. The health authority said most rates of lung and bladder cancers near the companies were “generally consistent with expected rates” over 15 years between 1999 and 2013.
But there was an increase in bladder cancer when narrowing in on the five-year period in North Portland.
State epidemiologist, Dr. Katrina Helberg, cautioned that the small number of cancers involved mean even a slight increase can result in a statistically significant outcome.
“At this point, we don’t have any evidence that the exposures that have been happening in these neighborhoods are resulting in any increases in cancer,” Helberg said.
She also said the increase was not sustained in subsequent years.