Irving Oil has told regulators that recent air quality testing it commissioned around its oil-by-rail terminal in Saint John, New Brunswick, Canada's largest such facility, shows no cause for public health concern.

Irving commissioned the study after it was flooded with complaints from residents of the eastern province's most populous city last winter about powerful smells wafting toward downtown when trains unloaded their cargoes.

All the pollutants measured in the study "were found to be below available regulatory objective limits," Irving said in a summary filed with the provincial Department of Environment and obtained by Reuters through a Right to Information Act request.

Oil-by-rail shipments have soared across North America in recent years as crude production outpaces pipeline capacity, raising worries about pollution and derailments.

The Saint John terminal was built in 2012 to serve Irving's 300,000 barrel per day refinery, a top gasoline supplier to New England. New Brunswick regulators approved it without requiring an environmental impact study.

Since its startup, the terminal has been blamed by residents for odors during open-air unloading of tanker cars. Also, several oil-laden trains serving it have derailed en route, including one that crashed in Lac-Megantic, Quebec, in 2013, killing 47 people.

Irving's air quality study, conducted by engineering firm Stantec, used standards used by other provinces because New Brunswick does not have ambient air quality limits for benzene, a known carcinogen found in oil, the documents said. It showed levels of benzene rose above Ontario's 24-hour limit in one out of six tests between March and July, and exceeded Alberta's one-hour limit in one out of 31 tests over the same period.

The summary also provided results for three other pollutants, none of which exceeded other provinces' limits, and said results collected for another 68 pollutants were withheld for the sake of brevity. A Stantec spokeswoman declined to provide the full study to Reuters. An Irving official did not respond to requests for comment.

Irving also told regulators it had not received any complaints from residents about odors from the facility since July, when it changed its rail car offloading procedures to keep tanker hatches closed.

In June, it received five odor complaint calls, including from two from residents so upset that they asked Irving to purchase their homes, according to Irving complaint logs filed with the Department of Environment.