Health hazards due to a cross-border bridge

Background

There are many studies in the environmental health and medical literature which demonstrate the health hazards to both children and adults of living close to busy roads. One of these analyses specifically concerns to a cross-border bridge in North America.

The US-Canada Peace Bridge

An epidemiologic analysis of health outcomes of the population in this region showed evidence of adverse health consequences in residents living nearby the border-crossing bridge. Oyana et al (2004) showed clearly that for adult residents living within 500m from the Peace Bridge in the U.S.-Canada border, the odds of having asthma were 4.4 times greater compared with residents living more than 2km away from the bridge. Lwebuga-Mukasa et al (2004) also demonstrated that health care use for asthma was significantly increased as the Peace Bridge’s traffic volume increased, which included a 65% increase in the number of trucks and buses over a ten-year period since its operation.

The authors of the report also stated that the trade corridor has increased prosperity but contributed significantly to air pollution particularly to nitrogen dioxide and particulate matter and this resulted in environmental and health impacts among residents in close proximity to the bridge.

Ambassador Bridge

Another study conducted by the US Environmental Protection Agency on the environmental impacts of the Ambassador Bridge, the busiest international commercial vehicle crossing in North America, showed the potential impacts of increased indoor levels of elemental carbon in surrounding residents due to downwind dispersion of diesel traffic associated with the bridge (Baxter et al 2008). The authors also reported a disproportionate health burden and environmental inequity among these residents living nearby the bridge.

What are the important implications for Hong Kong?

How much can we learn from the overseas experience when we look at the Hong Kong-Zhuhai-Macau Bridge (HZMB)? Significant harm to public health especially among those living nearby the HZMB can be expected if we are not able to provide sufficient mitigation and enforcement of controls. This could or should include controls on certain vehicle specifications and types of fuel, with adequate monitoring, enforcement and heavy fines for violations.

Edited by AJH

References:

Oyana TJ, Rogerson P, Lwebuga-Mukasa JS. Geographic clustering of adult asthma hospitalization and residential exposure to pollution at a United States-Canada Border Crossing. American Journal of Public Health. 2004;94:1250-1257.

Lwebuga-Mukasa JS, Oyana T, Thenappan A, Ayirookuzhi SJ. Association between traffic volume and health care use for asthma among residents at a U.S.-Canadian border crossing point. Journal of Asthma. 2004;41:289-304.

Baxter LJ, Barzyk TM, Vette AF, Croghan C, Williams RW. Contributions of diesel truck emissions to indoor elemental carbon concentrations in homes in proximity to Ambassador Bridge. Atmospheric Environment. 2008;42:9080-9086.

World cities' air quality comparison using satellite data

Bad air in Hong Kong
Hong Kong, together with other east Asian cities, has some of the worst air quality in the world. In terms of high GDP per capita, Hong Kong is the worst performer. NASA data shows how far we have to go to make our air fit for breathing.

NASA satellite data
The most updated satellite data from NASA were retrieved. Based on aerosol optical thickness (AOT), the amount of light absorbed by particles in a defined area of atmosphere above different places on earth can be estimated. According to NASA, if the value of AOT is less than 0.1, visibility is the highest and a clear blue sky can be seen in daytime; on the other hand, if the value is 1, visibility is the worst and the sky is very hazy.

Measurements of aerosol particles at different heights of the atmosphere (<2 km, 2-4 km, >4 km) around the world, including East Asia and southern China, showed clearly that the closer to the ground the higher the density of aerosol particles. This indicates that using AOT to estimate near-ground particulate air quality caused by anthropogenic combustion is relevant and should be valued by policy-makers (Clarke and Kapustin 2010). We have also applied this kind of satellite data in epidemiologic studies and showed associations with damage to children’s respiratory system in Hong Kong (Lai et al 2010).

The AOT level in Hong Kong (Figure) in April 2011 was very high, indicating poor air quality with hazy sky conditions. Although it was slightly better than Guangzhou, Macau, and Bangkok (Thailand), it was even poorer than Shanghai and Beijing in China, as well as Seoul (South Korea), New Delhi (India), Mexico City (Mexico), Tokyo (Japan), and very much poorer than London (United Kingdom), Paris (France), Athens (Greece), New York (United States), Rome (Italy), Helsinki (Finland), and Sydney (Australia).

The monthly average PM₁₀ in April in 2011 in Hong Kong was 59 μgm^-3, higher than that last year (41 μgm^-3) and about 200% above the World Health Organization guideline for safer air quality. If AOT is linearly associated with particulate concentration (Lai et al 2010), the AOT level in April corresponding to the WHO annual AQG level of 20 μgm^-3 should be approximately around 0.27 (dotted line). In Hong Kong, it is over 0.8.

The latest epidemiologic evidence from other regions showed that exposures to particulates and ozone were associated with increased inflammation in early pregnancy (Lee et al 2011), potentially damaging the mother and unborn child. Exposure to SO₂ and PM₁₀, much elevated pollutants in Hong Kong, particularly during the first 3 months of pregnancy, may increase risk of born-dead foetus (Hwang et al 2011). Serious harm to maternal and child health is a signal for urgent and effective action by government to protect the public's health. It is clear this is not yet happening in the HKSAR.

Air quality in Hong Kong at present cannot protect our health at all. We should not allow the impression to be created that Hong Kong has acceptable air quality or that it is comparable to other jurisdictions with better air quality.

Edited by AJH

References:

Clarke A, Kapustin V. Hemispheric Aerosol Vertical Profiles: Anthropogenic Impacts on Optical Depth and Cloud Nuclei. Science. 2010;329:1488-1492.

Lai HK, Ho SY, Wong CM, Mak KK, Lo WS, Lam TH. Exposure to particulate air pollution at different living locations and respiratory symptoms – an application of satellite information. International Journal of Environmental Health Research. 2010;20:219-230.

Lee PC, Talbott EO, Roberts JM, Catov JM, Sharma RK, Ritz B. Particulate Air Pollution Exposure and C-reactive Protein During Early Pregnancy. Epidemiology. 2011 Apr 21. [Epub ahead of print]

Hwang BF, Lee YL, Jaakkola JJ. Air Pollution and Stillbirth: A Population-Based Case-Control Study in Taiwan. Environ Health Perspect. 2011 Mar 28. [Epub ahead of print]