The Health Risks Of Tunnel Emission Stacks

Effect of vehicle exhausts on human health

Air pollution from vehicle exhausts is among the main contributors to pulmonary and cardiovascular diseases globally. Human contact with vehicle exhausts occurs to pedestrians walking along the roads as well as the drivers and commuters in the vehicles on the road. This contact is more for people who live or work in areas that are continuously exposed to vehicle exhausts. These areas include residential and work places with close proximity to the roads and tunnel emission stacks for road tunnels.

The congestion of roads has necessitated innovations in the transport sector. Among these innovations is the construction of road tunnels underground. Similar to when vehicles use surface road, in the road tunnels the vehicles also produce exhaust fumes. In order to ensure good air quality in the road tunnels, stacks are constructed to ventilate the tunnels. The stacks connect the tunnels to the surface, allowing for the escape of the vehicle emissions into the atmosphere.

The road tunnels are exposed to risks such as water inrush. This is the sudden flooding of water into the road tunnels (Li, et al., 2016). The construction specifications for the tunnels are the biggest factors in determining whether it is going to be exposed to incidents such as water inrush. The construction of the tunnels should be done in a manner that enables it to handle any hazardous event (Bubbico, et al., 2009 ).  

The tunnel emission stacks pose a health risk due to the resultant air pollution. This is especially during traffic jams, when the pollution levels are at their highest (Bari & Naser, 2010). Other than the health risks that may range from persistent coughs to lung cancer, the environment is also affected. The environment around the tunnel emission stacks changes, and with continuous emissions it becomes characterised by reduced animal and plant life (AECOM Australia Pty Ltd, 2014).

Numerous research works such as (Cowie, et al., 2012) have been done to investigate the effects that the air quality resulting from the emissions from the tunnel emission stacks has on the communities living near them. This research paper builds on this to provide a more detailed comparative analysis to determine the extent of the effects of the air quality on communities living near tunnel emission stacks.

The results for the research are presented in table 1 and table 2 below:

 

Table 1

Table 2

The research was carried out during the three-year period between 2006 and 2008. The data was collected from a total of 3358 individuals. 2978 individuals contributed to information in table 1, while the remaining 380 contributed to information in table 2.

Road tunnels and their ventilation systems

The research presented data from four different zones. The four zones had differing exposures to the tunnel emissions, this allowed for effective comparison to determine impacts of the air quality resulting from the presence of the tunnel emission stacks.

The four zones were:

1. Reduced Exposure Zone.
2. Increased Exposure Zone.
3. Eastern Stack Zone.
4. Control Zone.

For the information presented in table 1, the demographics and symptoms of the respondents were recorded. This information was collected on the following variables for each of the four zones of study during the three-year period:

1. Age 
2. Gender
3. Asthma Diagnosis.
4. Current Asthma Prevalence.
5. Instances of inhaled corticosteroids.
6. Wheeze Prevalence.
7. Cough Prevalence.
8. Uptake of asthma medication.
9. Instances of Upper Respiratory Symptoms.
10. Instances of Lower Respiratory Symptoms.
11. Instances of severe Lower Respiratory Symptoms.
12. Instances of Mouth Symptoms.
13. The Rate of Smoking.
14. Home Environment Factors such as;
15. Usage of Unflued Gas Heater.
16. Usage of Gas Cooktop or Oven.
17. ETS at Home.
18. Educational status (Tertiary Educated, High School/Diploma and Up to Middle School).
19. Work Status (Paid Work or not).

For the information presented in table 2, responses were recorded for the frequency of the occurrence of symptoms among the respondents. This information was collected on the following variables for each of the four zones of study during the three-year period:

1. Number of days during which symptoms were present.
2. Frequency of day-time symptoms.
3. Frequency of night-time symptoms.
4. Number of days during which respondent experienced wheezing.
5. Number of days during which respondent experienced coughing.
6. Number of days during which respondent used bronchodilator.
7. Number of days during which upper respiratory symptoms were present.

For the instances where data was not available, such as when the respondent was unwilling to respond to a question(s), the missing entry was considered into the nearest most likely response.

Generally, there was a decrease in the number of respondents in the study across all the four zones over the three-year period. This true for both the demographics and symptoms subset in table 1 and the subgroups subset in table 2.

The number of respondents aged 18 years and above also decreased for three of the zones with the exception of the Control Zone where the number was unchanged at 72%. The number of female respondents on the other hand had an overall increase across the four zones in the three-year period.

From the first dataset in tables 1, the Diagnosed Asthma, Current Asthma and the Lower Respiratory Symptoms in the reduced exposure rose from 2006 to 2007 and thereafter remained unchanged. The rises were from 18% – 20%, 11% – 13% and 39% – 47% respectively.  

There is a consistent increase in the Inhalation of Corticosteroids and in the use of Asthma Medication. Also, the Cough, Severe Lower Respiratory Symptoms and Mouth Symptoms also consistently increase over the three-year period.

The Wheeze and the Upper Respiratory Symptoms both rise from 2006 to 2007, then drop in 2008.

From the second dataset in table 2, the number of symptom days and the frequency of the night-time symptoms generally decrease form 2006 – 2007. However, the day-time symptoms, Wheeze, Bronchodilator Use, Cough and Upper Respiratory Symptoms fall from 2006 to 2007, then rise in 2018. 

From the first dataset in table 1, the Asthma Medication and Mouth Symptoms rise from 2006 – 2007 then remained unchanged. The rises were from 11% – 14% and 9% – 21% respectively.

Water inrush and risks associated with tunnel construction

The Diagnosed Asthma, Current Asthma, Wheeze, Cough, Lower Respiratory Symptoms, Severe Lower Respiratory Symptoms and Inhaled Corticosteroids rise from 2006 to 2007 then fall again in 2008. The Upper Respiratory Symptoms was the only variable that had a consistent rise.

From the second dataset in table 2, all the data variables indicate a fall from 2006-2007, then followed by a rise in 2018.

From the first dataset in table 1, the Current Asthma increases from 9% in 2006 to 12% in 2007, thereafter remains unchanged for 2008.

The Diagnosed Asthma, Cough and Lower Respiratory Symptoms increase consistently from 2006 to 2008.

The Wheeze, Asthma Medication, Inhaled Corticosteroids, Severe Lower Respiratory Symptoms, Upper Respiratory Symptom and Mouth Symptoms exhibit a rise from 2006 to 2007, then fall in 2008.

From the second dataset in table 2, the Wheeze and the Upper Respiratory Symptoms consistently rise from 2006 to 2018. The Day-time Symptoms on the other hand consistently decrease from 2006 to 2018. However, the trends for Symptoms, Night-time Symptoms, Bronchodilator and Cough have undefinable trends.    

From the first dataset in table 1, the Wheeze and the Lower Respiratory Symptoms rise from 2006 to 2007, then remain unchanged in 2008. The increases were from 10% to 13% and 33% to 43% respectively. On the other hand, Inhaled Corticosteroids remain unchanged from 2006 to 2007, but rises from the initial 5% to 7% in 2008.

The Diagnosed Asthma, Asthma Medication, Cough, Severe Lower Respiratory Symptoms and Mouth Symptoms consistently rise from 2006 to 2008.

The Current Asthma and the Upper Respiratory Symptoms rise from 2006 to 2007, then fall in 2008.

From the second dataset in table 2, the Upper Respiratory Symptoms consistently rise from 2006 to 2008.  On the other hand, the Wheeze consistently decrease over the same period.

The Bronchodilator Use rises from 2006 to 2007, then falls in 2008. The Symptoms, Night-Symptoms, Day-Symptoms and Cough fall from 2006 to 2007, then rises in 2008.

Conclusion

This research finds more occurrences of the symptoms are present among the respondents in the Increased Exposure and the Eastern Stack Zones. The comparison between the percentage of symptoms among individuals in the Reduced Exposure and Control Exposure Zones reveal that the mitigation measures have not reduced occurrence of symptoms in the Reduced Exposure Zone to the level of the Control Exposure Zone. We hence conclude that the tunnel emission stacks pose a health risk to individuals living around them. Also, we conclude that the mitigation measures put in place have made very little difference, thus better measures should be put in place.

Further research should focus on collection of more data to increase the accuracy of the findings, preferably over a longer period of time. The short time period presents a constraint in carrying out efficient and reliable analysis. 

References

AECOM Australia Pty Ltd, 2014. Environmental Impact Statement Section 2.4-2.7 pp. 51-59, Sydney: NorthConnex Submissions and preferred infrastructure report.

Bari, S. & Naser, J., 2010. Simulation of Airflow and Pollution Levels Caused by Severe Traffic Jam in a Road Tunnel. Tunnelling and Underground Space Technology , 25(1), pp. 70-77.

Bubbico, R., Di Cave, S., Mazzarotta, B. & Silvetti, B., 2009 . Preliminary Study on the Transport of Hazardous Materials Through Tunnels. Accidents Analysis and Prevention, 41(6), pp. 1199-1205.

Cowie, C. T. et al., 2012. Respiratory Health Before and After Opening of a Raod Traffic Tunnel: A Planned Evaluation. PLoS ONE, 7(11).

Li, L. et al., 2016. Mechanism of Water Inrush in Tunnel Construction in Karst Area. Geomatics, Natural Hazards and Risks, 7(1), pp. 35-46.