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]

Local emission rather than weather with poor wind

Pollution levels and wind speeds
This figure shows the level of a traffic-related air pollutant, nitrogen dioxide (NO₂), recorded by EPD urban rooftop and roadside monitors as well as by a rural background monitor in Tap Mun (Grass Island) in 2009. NO₂ daily average concentrations in Autumn (Sept to Nov) were grouped together by three levels of wind-speed: “Low”, “Medium” and “High” were defined as days with wind-speed lower than the 25^th percentile, from the 25^th to 75^th percentile, and higher than the 75^th percentile in the year respectively. Point estimates of the mean NO₂ concentrations and the 95% confidence intervals are shown in the figure. Similar patterns were found among other seasons of the year and other pollutants.

Our results indicate clearly that in the absence of traffic emissions, as in the location of the rural background monitor in Tap Mun, air quality could be well below (that is, compliant with) the WHO annual AQG of 40 μgm^-3. However, in the presence of traffic emissions, the concentrations of NO₂ far exceeded the safer WHO guideline by up to 300% on days with poor wind dispersion. Although air pollution levels were lower on days with higher wind-speeds, the 50% reduction due to windy weather effect was very small when compared with the 1200% reduction due to removal of traffic emissions.

Epidemiologic evidence just published in the past few months shows that exposure to vehicular source pollutants (including NO₂ and black carbon) increases the risk of blood cancer in children (Amigou et al 2010) and shortening of genetic sequences in human body cells (McCraken et al 2010), which is a cause of cell replication problems leading to aging, heart disease, and cancers.

Attributing our air quality problems to regional or meteorological reasons cannot help in achieving the WHOAQG and improve public health. The wind only blows Hong Kong's pollutants into our neighbours' backyard.

Edited by AJH

References:

Amigou A, Sermage-Faure C, Orsi L, Leverger G, Baruchel A, Bertrand Y, Nelken B, Robert A, Michel G, Margueritte G, Perel Y, Mechinaud F, Bordigoni P, Hémon D, Clavel J. Road Traffic and Childhood Leukemia: The ESCALE Study (SFCE). Environ Health Perspect. 2011 Apr;119(4):566-72. Epub 2010 Dec 8.

McCracken J, Baccarelli A, Hoxha M, Dioni L, Melly S, Coull B, Suh H, Vokonas P, Schwartz J. Annual ambient black carbon associated with shorter telomeres in elderly men: Veterans Affairs Normative Aging Study. Environ Health Perspect. 2010 Nov;118(11):1564-70.

The new proposed AQO won't protect health

The proposed HKSAR AQO are not fit for health protection
The government’s repeated emphases on benchmarking the WHO Air Quality Guideline (AQG) is misleading because, except for the annual AQG for NO₂, none of them are directly derived from WHO. According to the WHO, all short-term AQG for gaseous pollutants (NO₂, SO₂, O₃) should not be exceeded once in a year and the AQG for particulate matter (PM₁₀ and PM_2.5) should not be exceeded on more than three days a year. The government’s proposed Hong Kong Air Quality Objectives (HKAQO) with adoption of "interim targets" or any limit values higher than the full WHO guideline values, or additional lax arbitrary modifications of allowable exceedances, will only create pseudo air quality limits that will never protect our heart, lungs and other body systems. Most importantly lax air quality controls will compromise child health with life time consequences for those affected.

We have demonstrated, in a recent analysis and publication, that two proposed HKAQO (PM_2.5 and SO₂) are either even worse than the most permissive WHO limits (only intended as entry level targets for poor low technology developing countries) or even poorer than the air quality in Hong Kong in 2010. In other words there is little or no scope for improvement through compliance with the new objectives. (www.hku.hk/press/news_detail_6375.html).

We can also show that the WHOAQG for NO₂ is very unlikely to be achievable in Hong Kong because the government proposes to permit an increased number of exceedances of the 1 hour limit, leading to discordance between the short- and long-term limits (Lai et al 2010). These contrived new limits are not evidence based and will not work to improve air quality in Hong Kong's highly polluted environment. The HKSAR government should also learn critically from overseas experience and avoid attempts to reinvent invalid decision rules (the new AQO), which are only intended to accomodate (that is legitimate) Hong Kong's high pollution in terms of the air pollution control ordinance.

Edited by AJH

Reference:

Lai HK, Wong CM, McGhee SM, Hedley AJ. Assessment of the health impacts and economic burden arising from proposed new air quality objectives in a high pollution environment. Open Epidemiology. 2011;4:106-122. http://www.benthamscience.com/open/toepij/articles/V004/SI0001TOEPIJ/106TOEPIJ.pdf

Exceedances of WHO Air Quality Guidelines in 2010

Summary of World Health Organization (WHO) Air Quality Guideline (AQG):
PM₁₀ 24-hr mean of 50 μgm^-3 & annual mean of 20 μgm^-3,
NO₂ 1-hr mean of 200 μgm^-3 & annual mean of 40 μgm^-3,
SO₂ 24-hr mean of 20 μgm^-3 & annualized mean of 5 μgm^-3,
O₃ maximum 8-hr mean of 100 μgm^-3 & annualized mean of 23.5 μgm^-3

WHO guidelines do not indicate totally safe air quality, only safer air. Hong Kong's pollutant levels violate the safer WHO limits on most days of the year. This analysis indicates the frequency and magnitude of the problem.

In Year 2010, monthly pollutant concentrations at all urban monitoring stations violated the expected WHO annual limits during cool season (January to March and October to December). This indicates there was no effective protection to public health (Figure). Among all 14 monitoring stations, only the Eastern station in July showed that air quality complied with the annual AQG of PM₁₀ and NO₂ and with the expected annual limit for SO₂ and O₃. All other stations, in all months of the year, showed violations of either single or multiple guidelines for the four criteria pollutants.

Daily or hourly pollutant concentrations at urban monitoring stations also frequently violated the WHO short-term AQG, mostly during the cool season for PM₁₀, NO₂ and O₃ and warm season for SO₂ (Figure). Among all 14 stations, Eastern station has the least number of days exceeding any of the WHO short-term AQG of the four criteria pollutants (128 days), followed by Tai Po (132 days), Kwun Tong (137 days), Yuen Long (152 days), Tung Chung (152 days), Central/Western (157 days), Sha Tin (167 days), Sham Shui Po (169 days), Tsuen Wan (183 days), Mongkok (184 days), Tap Mun (191 days), Central (207 days), Kwai Chung (231 days) and Causeway Bay (256 days).

These large numbers of days on which the air was unsafe to breathe, because of violation of the minimum standard for health protection, show that everyone in Hong Kong has a very high exposure to toxic chemicals which cause diseases of the lungs, heart, and blood vessels. They also cause health problems in diabetics, in pregnant mothers, the sick, elderly and poor.

Edited by AJH

What are the Air Quality Objectives?

Air Quality Objectives are intended to protect the environment and human health. Through legal instruments such as the Environmental Impact Assessment Ordinance, we should be able to limit new sources of pollution which will degrade air quality and cause harm to sensitive receivers such as children. Air pollution potentially affects everyone in both the short and long term.

The HKSAR government has not revised the existing Hong Kong Air Quality Objectives (HKAQO) since they were established in 1987, despite updates of the WHOAQG in 2000 and 2005. The data in 1987 was based on research which dated back to the early 1980s. So our AQO are really 30 years out of date.

The more recent WHO updates were both based on comprehensive reviews of epidemiologic evidence on air pollution effects to identify the minimum air quality requirements to protect human health and well-being. The outdated 1987 HKAQO are set too high with little relevance to current scientific evidence on limits needed to protect public health. For example, the daily (24 hour average) SO₂ limit of 350μgm^-3 is 17 times above the present WHOAQG for a 24 hour average of 20μgm^-3.

In 2009, the HKSAR government proposed new HKAQO based mainly on the most lax of the WHO air quality limit, the so-called "interim targets". These “interim targets” were designed for low income developing regions to provide a preliminary basis for an air quality improvement strategy. They are not intended as guidelines for a high GDP per capita region like the HKSAR. For example, the government’s proposed new AQOs for SO₂, PM_2.5 and O₃ are based on the “entry level” Interim Target 1 (IT-1). The lax limit for PM₁₀ is based on the second WHO Interim Target 2 (IT-2) with an annual limit of 50μgm^-3, which is only slightly better than the previous Hong Kong AQO of 55μgm^-3, which was introduced more than two decades ago.

The question is why did the government's consultants set such lax limits and ignore the opportunity to set notional standards which would drive meaningful improvement of air quality? The lack of a clear strategy to improve air quality is clearly reflected by the government’s selection of the most lax limits available as the basis for the proposed new HKAQO.

In fact, the proposed HKAQO are even worse than the selected WHO lax limits because these WHO advisories have been further modified by adding additional days of allowable exceedances above the short-term limits, so that the long-term annual limits may actually shift to even higher levels than the original selected WHO limits.

Our latest analyses show that the proposed new HKAQO of 125μgm^-3 for SO₂ could lead to annual SO₂ concentrations even higher than the current mean concentrations (Lai et al 2010). This is a clear and alarming signal that public health impacts were not properly considered when setting the new AQO. The government's strategy lacks any elements of a precautionary approach; this has serious implications for the future health of children and others most vulnerable to air pollution.

Edited by AJH

Reference:

Lai HK, Wong CM, McGhee SM, Hedley AJ. Assessment of the health impacts and economic burden arising from proposed new air quality objectives in a high pollution environment. Open Epidemiology. 2011;4:106-122. http://www.benthamscience.com/open//toepij/articles/V004/SI0001TOEPIJ/106TOEPIJ.pdf

Update: Evidence of harmful health effects (Nitrogen Dioxide)

Human population studies in 2010 showed that exposure to NO₂ was associated with several bad health outcomes including increased risk of congenital heart defects (Vrijheid et al 2010), lower infant birth weight (Lepeule et al 2010, Darrow et al 2010), post-menopausal breast cancer in women (Crouse et al 2010), impairments in children’s lungs especially among genetically susceptible persons (Breton et al 2010), increased risks of developing childhood asthma (Clark et al 2010), exacerbated wheezing among asthmatic children (Mann et al 2010), and increased acute childhood leukaemia among those living nearby heavy-traffic road (within 500 meters) or chronically exposed to more than 27.7μgm^-3 of NO₂ (Amigou et al 2010).

Earlier epidemiologic evidence quoted by WHO showed the adverse health effects of NO₂ on daily mortality, children’s hospital admissions for asthma, emergency visits due to ischaemic heart disease, chronic obstructive pulmonary disease and asthma, lung cancer, preterm birth, foetus growth retardation, and sudden infant death (WHO 2006).

Apart from the health effects attributable to exposure to NO₂, other recently reported health effects of exposure to this pollutant include increased infant mortality risks (Son et al 2010), narrowed arteries in the retina (Adar et al 2010), atherosclerosis (Bauer et al 2010), cardiovascular mortality (Guo et al 2010), inflammation of the middle ear in infants (Macintyre et al 2011), damage to DNA (Ren et al 2010), all-causes of mortality and specifically, respiratory and lung cancer deaths (Hales et al 2010), childhood bronchial hyper-reactivity and asthma (Carlsten et al 2010), emergency hospital visits for hypertension (Guo et al 2010), hospital admissions for ischaemic stroke (Andersen et al 2010), daily mortality (Kan et al 2010) and altered cardiac autonomic function (Wu et al 2010).

While we must be cautious about attributing bad health outcomes to a single pollutant in environments where several pollutants are raised, the accumulating weight of evidence suggests that NO₂ levels are an important indicator of health risks. Urgent and effectice action is needed to reduce all emissions including NO₂ and volatile organic compounds. 

Edited by AJH

Reference:

Vrijheid M, Martinez D, Manzanares S, Dadvand P, Schembari A, Rankin J, et al. Ambient Air Pollution and Risk of Congenital Anomalies: A Systematic Review and Meta-Analysis. Environ Health Perspect. 2010. [Epub ahead of print].

Lepeule J, Caïni F, Bottagisi S, Galineau J, Hulin A, Marquis N, et al. Maternal exposure to nitrogen dioxide during pregnancy and offspring birth weight: comparison of two exposure models. Environ Health Perspect. 2010;118:1483-9.

Darrow LA, Klein M, Strickland MJ, Mulholland JA, Tolbert PE. Ambient Air Pollution and Birth Weight in Full-Term Infants in Atlanta, 1994-2004. Environ Health Perspect. 2010. [Epub ahead of print].

Crouse DL, Goldberg MS, Ross NA, Chen H, Labrèche F. Postmenopausal Breast Cancer is Associated with Exposure to Traffic-related Air Pollution in Montreal, Canada: A Case-Control Study. Environ Health Perspect. 2010. [Epub ahead of print]

Breton CV, Salam MT, Vora H, Gauderman WJ, Gilliland FD. Genetic Variation in the Glutathione Synthesis Pathway, Air Pollution, and Children's Lung Function Growth. Am J Respir Crit Care Med. 2010. [Epub ahead of print].

Clark NA, Demers PA, Karr CJ, Koehoorn M, Lencar C, Tamburic L, et al. Effect of early life exposure to air pollution on development of childhood asthma. Environ Health Perspect. 2010;118:284-90.

Mann JK, Balmes JR, Bruckner TA, Mortimer KM, Margolis HG, Pratt B, et al. Short-term effects of air pollution on wheeze in asthmatic children in Fresno, California. Environ Health Perspect. 2010;118:1497-502.

Amigou A, Sermage-Faure C, Orsi L, Leverger G, Baruchel A, Bertrand Y, et al. Road Traffic and Childhood Leukemia: The ESCALE Study (SFCE). Environ Health Perspect. 2010. [Epub ahead of print].

World Health Organization (WHO). Air Quality Guidelines Global Update 2005: particulate matter, ozone, nitrogen dioxide and sulfur dioxide. Copenhagen: WHO Regional Office for Europe. 2006.

Adar SD, Klein R, Klein BE, Szpiro AA, Cotch MF, Wong TY, et al. Air Pollution and the Microvasculature: A Cross-Sectional Assessment of In Vivo Retinal Images in the Population-Based Multi-Ethnic Study of Atherosclerosis (MESA). PLoS Med. 2010;7:e1000372.

Bauer M, Moebus S, Möhlenkamp S, Dragano N, Nonnemacher M, Fuchsluger M, et al. Urban particulate matter air pollution is associated with subclinical atherosclerosis: results from the HNR (Heinz Nixdorf Recall) study. J Am Coll Cardiol. 2010;56:1803-8.

Guo Y, Barnett AG, Zhang Y, Tong S, Yu W, Pan X. The short-term effect of air pollution on cardiovascular mortality in Tianjin, China: comparison of time series and case-crossover analyses. Sci Total Environ. 2010;409:300-6.

Macintyre EA, Karr CJ, Koehoorn M, Demers PA, Tamburic L, Lencar C, et al. Residential Air Pollution and Otitis Media During the First Two Years of Life. Epidemiology. 2011;22:81-89.

Ren C, Fang S, Wright RO, Suh H, Schwartz J. Urinary 8-hydroxy-2'-deoxyguanosine as a biomarker of oxidative DNA damage induced by ambient pollution in the Normative Aging Study. Occup Environ Med. 2010. [Epub ahead of print].

Hales S, Blakely T, Woodward A. Air pollution and mortality in New Zealand: cohort study. J Epidemiol Community Health. 2010. [Epub ahead of print].

Carlsten C, Dybuncio A, Becker A, Chan-Yeung M, Brauer M. Traffic-related air pollution and incident asthma in a high-risk birth cohort. Occup Environ Med. 2010. [Epub ahead of print].

Guo Y, Tong S, Zhang Y, Barnett AG, Jia Y, Pan X. The relationship between particulate air pollution and emergency hospital visits for hypertension in Beijing, China. Sci Total Environ. 2010;408:4446-50.

Andersen ZJ, Olsen TS, Andersen KK, Loft S, Ketzel M, Raaschou-Nielsen O. Association between short-term exposure to ultrafine particles and hospital admissions for stroke in Copenhagen, Denmark. Eur Heart J. 2010;31:2034-40.

Kan H, Wong CM, Vichit-Vadakan N, Qian Z; PAPA Project Teams. Short-term association between sulfur dioxide and daily mortality: the Public Health and Air Pollution in Asia (PAPA) study. Environ Res. 2010;110:258-64.

Wu S, Deng F, Niu J, Huang Q, Liu Y, Guo X. Association of heart rate variability in taxi drivers with marked changes in particulate air pollution in Beijing in 2008. Environ Health Perspect. 2010;118:87-91

Increasing air pollution from the roads

Traffic pollution creates one of the biggest hazards to health in Hong Kong. Roadside pollutant levels affect at least 60% of the population. The evidence is clearly provided by the EPD monitors but there is no commensurate action by government to protect health.

The trend of nitrogen dioxide (NO₂) levels at roadside stations, as shown by the levels at Central station (Figure), is currently rising higher every year. In December 2010, the monthly average concentration in Central (162μgm^-3) reached the highest monthly record since the station has been in operation. This level exceeded by 300% the World Health Organization Air Quality Guideline annual limit for NO₂ of 40μgm^-3 and represents the near-ground air quality, which contributes to more than 60% of the exposure of the Hong Kong population to air pollutants (Lai et al 2010).

This increasing trend of urban roadside NO₂ was clearly due to emissions from local urban traffic and not due to the emissions dispersed from across the border. There was no upward trend in the background or regional ambient NO₂ levels during the same period (Figure). NO₂ concentrations at Tap Mun (Grass Island) are consistently low in that traffic free environment.

Traffic pollution is major threat to public health and both particulate and nitrogen dioxide levels, especially in the cool season, indicate that abatement measures are failing to produce improvements on an acceptable timescale.

Edited by AJH

Reference:

Lai HK, Wong CM, McGhee SM, Hedley AJ. Assessment of the health impacts and economic burden arising from proposed new air quality objectives in a high pollution environment. Open Epidemiology. 2011;4:106-122. http://www.benthamscience.com/open//toepij/articles/V004/SI0001TOEPIJ/106TOEPIJ.pdf