Air quality protection under full review
Napthalene incident prompts steps to improve system
In her letter of June 19 (Weekend Feedback: Monitoring Falls Short in Ensuring Air Quality), Marlene Kane makes a valid point. Detailed lab analysis of a 24-hour air sample collected May 27 at the perimeter of the coke ovens site showed naphthalene in excess of our site standards. But real-time spot checks on the same day by hand-held devices did not reveal a problem that would warrant a shutdown.
This is as much a concern to us as it is to Ms. Kane. It is the reason we stopped work at the Domtar tank, pending a thorough review of several aspects of the cleanup project, including:
Cleanup work at the Domtar tank will not resume until all these reviews are completed to our satisfaction and that of the Nova Scotia Department of Environment and Labour and the district medical officer of health.
We see this as an opportunity to refine and improve all these systems. We are confident that it will result in better systems that are more useful to project managers, regulators, and the people of Sydney.
It is important to recognize, however, that air monitoring technology has limits. One obvious limit is the inevitable trade-off between timeliness and precision.
The canisters we use to collect 24-hour air samples for laboratory analysis produce highly precise measurements of more than 50 chemicals at the very limits of detectability - from a few parts per billion to less than one part per trillion. But it takes a week to get the results back from the lab.
Real-time monitors that produce instantaneous results measure far fewer chemicals, with much less precision a few parts per million or per 10 million. Different equipment may be able to narrow this gap - that is something our review will tell. us - but may not close it altogether.
It is also important to recognize that events having nothing to do with the tar ponds or coke ovens can cause air samples to exceed our stringent site guidelines. We measure minuscule quantities. Trucks rumbling down Frederick Street on hot, dusty days can send readings beyond prescribed limits. So can coal trains.
In July 2002, forest fires in Quebec, more than 1,200 kilometres away, caused particulate matter in the air over Sydney to soar above site standards for days on end.
Every excess reading has to be evaluated on a case-by-case basis, taking account of all the circumstances and using common sense.
Common sense suggests that the current episode be kept in reasonable perspective. Naphthalene is a common household chemical, found in mothballs that are available for sale at various stores in Sydney. Our air quality guidelines are stringent. Naphthalene was detected in excess of those standards only at the perimeter of the coke ovens site. Identical monitors operating at the same time in nearby residential neighbourhoods detected no excess naphthalene. Nor were an of the 50 other chemicals we test for detected in amounts that exceed guidelines.
We take our responsibility to control chemical emissions, including naphthalene, seriously. That's why the combination of circumstances in this case caused us to shut down an important project and keep it shut down until we get to the bottom of the problem and fix it.