The lungs are gas exchanging organs, taking in oxygen, which enables various cellular processes, primarily to create energy. They also expel carbon dioxide, which is a waste product of energy production. Oxygen is not stored in the body, therefore the continuous renewal of supply is required.
Lungs are made up of lobes. Two lobes on the left with space for the heart and three lobes on the right lung. The right lung is slightly larger than the left. Air enters the nasal and/or the oral cavity, into the windpipe (trachea), into the bronchus of each lung, bronchi, bronchioles, and finally in to the aveoli which are tiny cauliflower shaped sacks. The lungs are lined with fine hairs called cilia, which move debris and pathogens upwards and out of the lungs. The lining also has goblet cells, which produce mucus which help clear and protect the lungs.
Let’s look first at how the lungs deal with an acute inhalation of a non-radioactive toxic substance, then we will move on to the effects of radiation.
Acute exposure to toxins is sudden and noticeable in that the lungs might burn, our throats would itch or scratch, we would cough continuously and our airways might feel constricted and chest tighten, until the majority of the toxin had been expelled. All of these mechanisms are designed to reduce how much of the toxic substance makes its way in to our lungs.
Picking cadmium as an example. This element is used in the production of ‘batteries, alloys, coatings (electroplating), solar cells, plastic stabilizers, and pigments’. Acute exposure might occur in the manufacturing workplace. We can also be exposed to cadmium from the burning of fossil fuels in the environment and from smoking. This exposure is at much lower dosages but potentially over a prolonged period (chronic exposure). The immediate effects of high level acute exposure, though these might be slightly delayed by 4-8 hours, (Health Protection Agency) would be irritation to the lining of the lungs, ‘Dyspnoea, chest pain and muscle weakness may also occur. Pulmonary oedema, bronchitis, chemical pneumonitis, respiratory failure’.
Some definitions (chest pain, muscle weakness are self explanatory):
Dyspnoea is breathlessness/shortness of breath.
Pulmonary oedema is the filling of the lungs with excess fluid or mucus. As we can see from this paper, oedema is a result of respiratory distress and corresponding cytokine release, caused by inhalation of toxic substances, whether gases or particulates.
Bronchitis, in this case, is the swelling and inflammation of the lining of the bronchus, bronchi and bronchiols in response to airborne irritants. These parts of the lungs will also produce mucus. The lungs will attempt to expel the irritant laden phlegm through continuous coughing.
Chemical pneumonitis is the diagnosis for difficulty in breathing due to inhalation of inorganic or organic substance that causes these reactions above.
Respiratory failure occurs where there the lungs become unable to absorb enough oxygen and expel enough carbon dioxide to sustain normal bodily and cell functions. Carbon dioxide (CO2) can poison the body if it builds up, causing dizziness, nausea, headaches, sleepiness, fatigue/drowsiness, irregular heartbeat and twitching muscles. You might also feel a buzzing or bubbling sensation under the skin.
Lack of oxygen in the body is called hypoxemia. Signs of hypoxemia are cyanosis, which include blueness of the lips, fingernails, skin, gums and inner eyelids. The blue colour comes from the colour of blood when it is low in oxygen (deoxygenated). You would also see the same signs of CO2 poisoning as above.
If you search for any substance deemed to be toxic upon inhalation, the symptoms listed above are common across all of them, as per this paper on acute inhalation injury. Depending on how much a person is exposed to in one go, dictates severity of injury to the lungs, time required to heal and whether permanent injury is done. It can take months for lungs to recover from acute exposure to some toxic substances. Damage to other organs and systems may also be involved, including the heart, liver, kidneys, blood and brain.
Chronic low level inhalation poisoning can be much harder to notice, not least because immediate (acute) reactions may not be seen. Injury to lungs and other organs may be well advanced by the time poisoning is identified. Systemic inflammation, asthma, cancers, kidney and liver failure, even Alzheimer’s have been connected to low level chronic exposure to toxins, particularly through atmospheric pollution. This paper ‘The effects of outdoor air pollution on chronic illnesses’ also highlights the effects of atmospheric pollution on the cardiovascular system.
If this is how the lungs are harmed by chemical inhalation, what does radiation do differently? Anyone who knows someone who has had radiotherapy in their lung area may have have seen them develop radiation pneumonitis some time after treatment. Radiation effects are created in terms of dosage, time span over which that dosage is received and how large an area of the body is exposed. The slower and smaller the doses the slower damage will become evident, and some damage is not detectable for months or even years. If the gaps between doses and size of dose received is small enough, the body has a good chance of healing the damage.
There are three types of radiation we looked at in our last article. Gamma radiation, produced by elements such as Cobalt-60 (used in radiotherapy) can seep through body tissues, and is emitted in light waves. This means the usual mechanisms to alert the body that ‘poison’ is entering the body might not be there. The throat is not irritated by particles that cause a coughing reflex for example. Reports from our queries indicate that there might be a sensation of the throat closing up when exposed to gamma rays - a sort of allergic reaction - and also extreme dryness in the throat.
Alpha and Beta particles, which are produced alongside gamma rays, do however, irritate the airways, with a sudden intense tickle, which causes a continuous cough. The tickles would not always be in the same place and might move further in to the lungs.
Gamma rays, when they reach a cell, transfer their energy to an electron, which then travels through the cell and can damage the cell indirectly. Alpha and Beta particles also indirectly damage the cell, by transferring energy to molecules they pass by, causing molecules to break. Molecules in the cell form Reactive Oxygen Species (ROS), and Reactive Nitrogen Species (RNS) - different types of free radicals that damage elements of the cell. Cells contain around 70% water, and the splitting of water molecules by radiation makes up a large part of these reactive species. Radiation from Alpha and Beta particles can also cause direct damage to parts of the cell. The areas of the cell most vulnerable to damage are the cell membranes including nucleaus membrane (which holds DNA material) and the DNA strands themselves - see image below and read this article for more detail. Damage to the membranes can destroy the cell completely. Breaks in DNA, whether single strand or double, can cause mutations in the way cells reproduce for irradiated cells that remain.
Radiation scatters when it enters the body (Compton Scattering). It can also infect other cells in a process called Radiation Induced Bystander Effect. This occurs through a number of processes including ROS and RNS as mentioned above. This is illustrated here in the diagram of how cancer is treated with radiotherapy. Note that radiation-damaged/dead cells also release cytokines, which, if the lungs were exposed to high enough levels of radiation, would cause a cytokine storm. We have seen in Covid-19, that a cytokine storm in the lungs causes flooding with mucus, making breathing incredibly difficult.
The higher the doses of radiation received in a shorter period of time, the more the damage is evident in the form of acute injury. Some effects of radiation though are often delayed, partly because of how radiation works at a deep cellular level. We might see damaged skin but no other effects, until a certain level of radiation has built up. Damaged skin, or damage to the airways in the form of burning, are likely to occur from the direct effects of ionising particles. The cellular damage from indirect bystander effects is likely to occur over a longer period of time. Changes at a DNA level, when a cell mutates and reproduces, would occur over an even longer period of time. In addition, if there were metallic particles included in inhalation exposure, as we suspect there have been, the effects of radiation might be amplified.
Direct damage through low level but continuous chemical and radiation exposure could compromise gas exchange cells to almost every surface of the lungs. If the exposure were subtle enough, but in continued doses, it might only become evident when someone starts to feel dizzy through lack of oxygen, or experiencing headaches and other symptoms associated with hypoxia. At this point the damage might be extensive enough to create a critical condition in the patient’s health, through the inability to exchange enough gases in the lungs to maintain essential bodily functions. This would result in hospitalisation and potentially intensive care treatment. In the worst cases it could lead to death.
Coming up - the effects of radiation and chemical exposure on the Heart Part 2b