多伦多空气污染日渐令人担忧

当我们从国内污染严重的大城市来到加拿大后，难免会感叹，加拿大城市的不拥护，和国内大城市少见的白云蓝天。而事实是，加拿大的城市也正遭受着环境污染的折磨，特别在多伦多这种类型的大城市，空气污染日益成为公害。

环境部（Minister of the Environment）年年要发布多次空气污染警告。你也许会说，加拿大人也太大惊小怪了，目前的污染并不很严重，起码比起国内一些大城市，多伦多的空气质量是很不错的。那么事实是什么呢？

北美城市的空气污染与国内的并不太一样。国内城市，特别是北方的一些城市，尘粒污染严重，如北京春季严重的风沙天气;还有一些城市，是控制不严格的重工业 对城市的严重的空气污染。而在北美，长期以来，却主要是机动车辆排出的尾气污染。近10多年来，中国城市的尾气污染也越来越严重，所以国内很多城市的环境 空气质量十分令人担忧。

对多伦多和安省大部分城市来说，除了尾气是主要贡献者外，也有随风而至的来自美国北中部城市工业废气污染。

最近，多伦多公众卫生部和加拿大卫生部联合完成一项研究。根据这份报告，在多伦多，一天之中，只有早上7点以前和晚上8点以后，空气污染的程度是最低的。 这项报告历经四年，监测了多伦多平均小时水平的空气污染波动幅度（hourly fluctuations of air pollution）。

研究发现，一氧化碳（carbon monoxide）和二氧化氮（nitrogen dioxide）在交通高峰期，达到了最高浓度水平。汽车尾气排入量在早上6点就开始上升，在8点时达到高峰。臭氧（Ozone）水平和二氧化硫 （Sulfur dioxide）在午后也达到高峰。至于灰尘颗粒，将可能是一整天都处于高水平，如果环境部公布这一天处于烟雾警告(smog alerts)期。

这些数据表明了什么？

肯定是与公众的身体康有关。但是，大家千万不要小瞧了这种警告。

比如，对那些喜欢进行户外锻炼者来说，以上数据就不是好消息。因为你不可能随时去户外跑步了，最好的时间是在早上7点以前和晚上8点以后，因为这两个时间 段空气污染水平最低。可是这两个时间段不是太早了一点，就是太晚了一点。这是没办法的事。因为你生活在这个污染日深的城市里，这是世界性趋势，不仅仅是多 伦多的问题。

但是也并不是没有办法，你可以尽量在户内完成你的锻炼，比如你可以迈着轻快的步子穿过一个一个商业大厦，因为这些地方巨大的中央空调可以过滤掉相当一部分户外的空气污染物。或者，选择哪些远离交通要道的公园和小径来完成你每日的长跑活动。

对于空气污染的加重，你也不要一味指责政府的无能。因为大家，在一意义上讲，都是同案犯。也许，我们应该做的是尽量减少使用汽车的使用频率，多用用公交系统。

作为日常健康常识，你要注意一下诸如咳嗽，胸痛，头痛，恶心及呼吸困难等症状，这些都是空气污染所能造成的疾病。

最后，我要提醒大家，还是务必关注一下，每日由环境部发布的空气污染警告。你可以到以下网址：
http://www.airqualityontario.com/alerts/signup.cfm
填入你的EMAIL地址，那么你就可以接收到来自他们的SMOG ALERTS了。

Heat, smog and exercise: Risky business?
CBC News Online | August 5, 2005
http://www.cbc.ca/news/background/exercise_fitness/

Toronto Public Health and Health Canada recently completed a study to identify convenient times of the day when it's safe for vigorous outdoor exercise.

Instead, researchers found that for most people, there really is no convenient time to go for that jog.

"In Toronto, pollution levels tend to be lowest overall … before 7 a.m. in the morning and after 8 p.m. in the evening," public health officials wrote.

The study measured hourly fluctuations of air pollution in Canada's largest city over a four-year period.

It found that carbon monoxide and nitrogen dioxide are at their highest levels during rush hour. The levels of these two pollutants, the product of car exhaust, begin rising at 6 a.m. and peak at 8 a.m.

Ozone levels meanwhile peak in the afternoon after sunlight has had a chance to "cook" a mixture of air-born nitrogen oxides and volatile organic compounds. Sulphur dioxide also peaks just after mid-day.

And levels of particulate matter, those tiny bits of pollution that get caught in your lungs, are high all day long during smog alerts.

"There's no time of the day when all pollutants together are at their lowest level, other than the deep dark night. And that's not very helpful," notes Monica Campbell, one of the report's authors and a medical toxicologist with the city of Toronto.

So unless you can exercise before 7 a.m. or after 8 p.m., your best bet is to head indoors, she says.

Toronto Rehab respirologist Michael Sarin agrees. "Air-conditioned buildings have filters [that trap pollution] and ozone doesn't penetrate inside buildings," says Sarin, who recommends his patients take a brisk walk through the mall on smog advisory days.

Sarin says the problem with outdoor exercise is that we breathe harder and take in more pollutants.

"The pollution by-passes the nose, which filters air pollution, and gets directly into the bronchial tubes, which causes deeper injury," he says.

Ozone penetrates bronchial tissue, sensitizing it so that other pollutants can then inflame the tissue, making it harder to breathe.

That's why it's important to know when you're at greatest risk for outdoor air pollution.

A smog watch is issued when there is at least a 50 per cent probability of smog within the next three days. A smog advisory is issued when there is a high probability of elevated smog levels within the next 24 hours, or if smog conditions happen without warning.

Naidoo also says everyone should pay attention to government air quality websites, such as Ontario's Ministry of the Environment.

Health experts say you should drink plenty of water, take frequent rests and pay attention to how your body feels.

Problems breathing, coughing, chest pain, nausea, headaches and weakness are your body's way of telling you to take it easy.

And try to exercise in parks or along low-traffic residential roads, which will keep you away from car exhaust.

And for goodness sake, don't drive to the park for your jog, says Sarin.

"We have to take personal responsibility for air pollution – reducing car use and taking public transit. You can't point the finger at government. We are the culprits," he says.

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