I can guess with high accuracy that your answer to the question of the image above is the Healthy Lung. If I guessed right, which I did, then I will advise you to be careful about what you breathe.

These are some gases that chemically poison the body’s oxygen transport systems, preventing oxygen from reaching the body tissues like the Carbon Monoxide CO, which combines with haemoglobin and blocks its ability to carry oxygen around the body, but there are some other gases that cause asphyxiation by producing severe irritation in the air passages and lungs like the Nitrogen Dioxide NO2.

NO2 dissolves in the moisture on any moist tissue surfaces, and forms strong acids or alkalis which then burn the delicate tissues. Health effects are related to its ability to dissolve in moisture to produce Nitric Acid which is a strong mineral acid.

Short term health effects:

• Eye irritation –stinging and watering
• Throat irritation – pungent smell, stinging nose & coughing
• Lung irritation – coughing, wheezing and tight chest – difficulty breathing
• Triggers asthma in asthmatics

The most intense effects occur after significant exposure.

• Acute pulmonary oedema

Fluid from damaged lung tissue pours out into air spaces preventing air from getting to deeper lung that causes choking aka asphyxia.

Pulmonary oedema may occur immediately with heavy exposure, but is more likely to be delayed usually for several hours after exposure.

Pulmonary oedema increases chest tightness and difficulty breathing and strong cough may occur.

Long term health effects:

• Asthma like a condition called RADS. Small air passages react, constrict and narrow, to any irritant (VOCs, smoke, cold air, etc).
• Obliterative bronchiolitis – the smallest air passages (bronchioles) are seriously scarred and become distorted & blocked.(chemicals, cigarette smoke, even cold air) may cause an asthma attack. The person becomes short of breath which can worsen over time.

“Safe” Levels

Air quality standards for NO2 and NOX as set out in the EU Ambient Air Quality Directive and WHO AQG
	EU Air Quality Directive		WHO AQG
Averaging period	Objective and legal nature	Concentration
1 Hour	Human health limit value	200 μg/m3 (100ppm) not to be exceeded on more than18 hours per year	200 μg/m3 (100ppm)
1 Year	Human health limit value	40 μg/m3 (20ppm)	40 μg/m3 (20ppm)
1 Hour	Alert threshold	400 μg/m3 (200ppm)
1 Year	Vegetation critical level	30 μg/m3 (15ppm)

Although both agencies EEA and EPA recommend 100ppm of 1 hour/daily exposure on NO2, the European Environment Agency recommends 20ppm on an Annual Mean but the Environmental Protection Agency recommends 53ppm on an Annual Mean.

Interesting observation, while I was searching for NO2 Pollution maps I couldn’t find results for the South hemisphere which led me on two possible conclusions. First the North hemisphere produces more NO2 or there isn’t enough research for the South hemisphere (Australia, Chile, Brazil, Argentina, South Africa etc…)!