Noxious Gases, Lethal Metals
Carbon Monoxide
Carbon monoxide is especially dangerous because it is a gas that is both colorless and odorless. The incomplete combustion of hydrocarbons releases carbon monoxide. It is readily absorbed by the lungs. Sources of carbon monoxide include poor ventilation, burning of fuels, cigarette smoking, and methylene chloride. Methylene chloride is found in paint thinner and can be absorbed through skin or inhaled. It is then metabolized to carbon monoxide.Carbon monoxide displaces oxygen. It has 200 times greater binding to hemoglobin than oxygen does. All organs need oxygen to function. The lack of oxygen affects the brain the most. Victims start to feel headache and nausea within 4 hours. Delayed effects include memory impairment.
The treatment for carbon monoxide poisoning is oxygen. The victim should be able to breath, so the airway must be intact. 100% oxygen may be required. In extreme cases, hyperbaric oxygen is needed to get the oxygen into the body. The person is placed into a chamber and exposed to 100% oxygen and increased atmospheric pressure.
Of course, the best thing would be to avoid any carbon monoxide exposure. Prevention is extremely important. Carbon monoxide detectors are life savers for a colorless and odorless gas. There should be proper ventilation of appliances, such as stoves, furnaces, and fireplaces. Also, cars should not idle in garages, especially garages attached to the home.
Cyanide
Cyanide is a chemical group made up of a carbon atom tripled bonded to a nitrogen atom. Cyanide salts - sodium cyanide and potassium cyanide - are used in several industries, including metal refining, jewelry cleaning, photography, and plastic manufacturing. Hydrogen cyanide is a colorless gas with a classic bitter almond odor. Unfortunately, approximately 60% of the population cannot smell the bitter almond odor.
The most common exposure to cyanide is smoke inhalation, especially due to house fires. The burning of materials like wool, silk, and rubber releases cyanide. Nail polish remover contains acetonitrile, which is metabolized to formaldehyde and cyanide inside the body. Outside the body, acetonitrile is nontoxic. The pits of fruit in the Prunus species contain amygdalin. If the pits are swallowed, the body converts amygdalin into glucose, aldehyde, and cyanide. So, never consume the pits of almonds, plums, peaches, nectarines, cherries, and apricots!
Why is cyanide poisoning a problem? Cyanide blocks the effects of multiple enzymes. The body is unable to use oxygen, even if there is plenty of oxygen available. The brain is especially affected by the inability to use oxygen. This presents as headache, confusion, tiredness, seizures, and possibly a coma. Cyanide may also have negative effects on the heart, lungs, and gastrointestinal tract. Cyanide concentrates in the blood and gives the skin a cherry red color.
Treatment of cyanide must be initiated immediately. A face mask is used to administer 100% oxygen. Cyanide does not bind to activated charcoal. The treatments for cyanide poisoning include a cyanide antidote kit or hydroxocobalamin.
The cyanide antidote kit contains amyl nitrite, sodium nitrite, and sodium thiosulfate. The nitrites generate methemoglobin. Cyanide has a high affinity for methemoglobin, so it no longer interferes with oxygen. In Europe, 4-dimethylaminophenol (4-DMAP) is preferred over sodium nitrite because methemoglobin is generated more quickly. Thiosulfate provides sulfur atoms to rhodanese, the enzyme involved in the elimination of cyanide.
Hydroxocobalamin is a metal complex containing cobalt. The cobalt atom combines with cyanide to form cyanocobalamin, better known as vitamin B12. However, hydroxocobalamin can turn urine and skin red.
Arsenic
The most well-known lethal metal is arsenic. It has no taste and no smell. Humans come in contact with arsenic through contaminated soil, water, or food. Arsenic leaches into soil and water from minerals, ores, and industrial wastes. Seafood, such as algae, fish, and shellfish, can contain arsenic. Arsenic particles may be lodged in the lungs, where they stay unabsorbed for years. Arsenic is more toxic when it is dissolved in liquid. It becomes an ion with a 3+ charge (trivalent arsenic) or a 5+ charge (pentavalent arsenic).Poisoning by arsenic presents with nausea, vomiting, and diarrhea as quickly as 10 minutes after exposure, but usually within a few hours. Arsenic is deadly because it affects the repolarization of the heart. The resultant abnormal heart beat does not provide oxygen to all organs efficiently. This often leads to the development of seizures.
The antidotes for arsenic poisoning are called chelating agents. Dimercaprol, also known as British antilewisite (BAL), is the first chelating agent. Arsenic forms bonds with the two sulfur groups in BAL. BAL is given as an injection. Another drawback is that BAL is formulated in peanut oil, so it cannot be used in people with a peanut allergy. It also causes a lot of nausea and vomiting. DMPS is a water-soluble analog of BAL. It is distributed by a German company. Succimer is the oral analog of BAL. It is preferred for later treatment of arsenic toxicity or chronic exposure to lethal metals.
Lead
Since the beginning of human societies, lead was a favored metal. It has a low melting point, making it easy to manipulate and form into objects. Lead-based paint has been dated as early as 40,000 BC. Before World War II, white paint was 50% lead in composition. More recently, in 2007, there was the infamous toy recall due to high levels of lead in paint. Some water pipes are lead, which is safe as long as only cold water runs through them. Hot water causes the pipes to leach lead into the water. Lead was once a component of gasoline, which introduced lead into the air. Lead was removed from gasoline in 1976, so the air is now mainly free of lead. Other sources of lead are cue stick chalk used in billiards and gunshot wounds. Any lead found in the body is due to environmental exposure because the body does not need lead to function.
Lead is absorbed by the gastrointestinal tract. The absorption of lead is increased if the person is fasting or deficient in zinc or iron. The body absorbs more lead thinking it is zinc or iron because they all have the 2+ charge. It is possible for lead to be absorbed through the lungs, but it does not go through skin. Lead is 99% bound to red blood cells. It also distributes to bone and soft tissues of the body (including the brain, kidney, and liver). For an adult, it takes several months to remove lead from the blood naturally. The time is even longer for children. Lead remains in parts of the bone for years.
The toxicity of lead is multifactorial. Since lead can have the same charge as calcium, it interferes with processes related to calcium and may stunt growth. Lead shortens the life span of red blood cells. It causes increased intracranial pressure and may cause memory losses, especially in children. Immediately after lead intoxication, the victim presents with odd behavior and loss of coordination. There is commonly persistent vomiting and decreased urine output. Mental effects include seizures and coma. Those with chronic lead toxicity are always tired due to dysfunctional red blood cells.
The treatment for lead toxicity is to remove the lead by using chelating agents. Calcium-disodium EDTA is one chelating agent. Lead takes the place of calcium in calcium-disodium EDTA and is excreted by kidney. Unfortunately, calcium-disodium EDTA has poor brain penetration. The antidotes for arsenic, BAL and succimer, can also be used in lead toxicity. Calcium-disodium EDTA and BAL are injections, while succimer is an oral agent and can enter the brain.
Iron
Iron has important functions in body as a component of hemoglobin and a great electron transporter. In the blood, iron is bound to transferrin. It is incorporated into hemoglobin in the bone marrow and stored as ferritin. Those who have iron deficiency may have to take iron supplements. The amount of elemental iron in various salts is listed in the table.
The body cannot directly excrete iron, so it is possible to have iron build-up. The toxicity of iron is due to the production of reactive oxygen species, which damage cell components. It takes 10-20 mg/kg of elemental iron to see toxic effects. Iron is irritating to the gastrointestinal tract, so intoxicated people experience nausea, vomiting, and abdominal pain. There may be blood in the vomit as well as the stool.
Iron binds poorly to charcoal, so treatment requires gut decontamination or whole bowel irrigation. The antidote for iron toxicity is dexferoxamine. It binds to the ferric (Fe3+) state of iron and turns the urine reddish-brown.