Column: From Chlorine to VX, a Primer on Chemical Weapons

  • This combination of satellite images provided by DigitalGlobe, a Maxar company, shows the Barzah Research and Development Center in Syria on Friday, April 13, 2018, top, and on Sunday, April 15, bottom, following a U.S.-led allied missile attack. The U.S., France and Britain launched missiles at Syrian military targets early Saturday, April 14, in response to an alleged chemical weapons attack near Damascus. (Satellite Image ©2018 DigitalGlobe, a Maxar company via AP) THE DIGITALGLOBE WATERMARK MAY NOT BE REMOVED

For the Valley News
Monday, April 16, 2018

Given the recent airstrike on Syria’s chemical weapons factories, the reader might be asking: Just what are these “chemical weapons?”

There are four categories of chemical warfare agents: choking, blister, lachrymatory and nerve.

The two major choking agents, chlorine and phosgene, literally choke the victim to death. These two gaseous chemicals cause the destruction of the membrane barrier that separates the blood supply from the lungs and the victim “drowns” internally as fluid (plasma) fills the lungs. Both chlorine and phosgene were employed in World War I by both sides.

Easily detected, chlorine smells like beach simply because bleach is an aqueous solution of chlorine.

Phosgene is more toxic than chlorine, and more insidious because it has the pleasant smell of newly mown grass (but which is a different chemical) and the effects are not immediately felt. Phosgene also destroys the lining of the lungs.

The most important blister agent is mustard “gas,” actually a volatile liquid like gasoline, which causes horrific burns, blisters, blindness and even death if exposure is excessive. The blisters are slow to heal and often become infected.

Mustard gas was used extensively in World War I and more recently in Syria and earlier in the Iran-Iraq war. It smells like garlic and is readily detected by its odor.

The other blister agent of note is “Lewisite,” synthesized in 1903 at Catholic University in Washington, D.C., but not used in World War I. This is the only chemical warfare agent to be first manufactured in the U.S.

Lachrymatory agents (tear gas) include CS (commonly known as pepper spray) and related chemicals that cause intense eye burning at very low concentrations, but little other toxicity. CS is the major riot-control agent that we see used by police on television. The other major tear gas is CN, known widely by the brand name Chemical Mace.

Interestingly, CS was discovered accidentally by a chemistry professor and his student at Middlebury College in 1928. Equally interesting is that seaweeds produce their own complement of natural tear gas agents, which are chemically related to mace and probably function as feeding deterrents toward fish.

The nerve agents include tabun, sarin, soman, VX and novichok, the first two of which were discovered in Germany during the late 1930s in a search for new insecticides by organic chemist Gerhard Schrader (with whom I once communicated). As required by the Nazi government, these agents were turned over to the Wehrmacht in Berlin, and were subsequently stockpiled by the Nazis, but never used in World War II. (The Nazi regime used the blood agent hydrogen cyanide, known as Zyklon B, as the killing agent in its concentration camp gas chambers.)

To circumvent the known antidotes to sarin and tabun, soman was synthesized in 1944 by biochemist Richard Kuhn, who earlier had won a Nobel prize in 1938 for his work with vitamins. Soman has the “distinction” of being immune to nerve gas antidotes, unlike sarin, tabun and VX.

Some 12,000 tons of tabun and perhaps 1,000 tons of sarin were discovered in 1945 at the end of World War II. The tabun plant was uncovered by the advancing Russians, dismantled, and reassembled in the Soviet Union on the Volga River and put into operation in 1946. Tabun became the standard Russian nerve agent. Two well-known sarin episodes are Saddam Hussein’s massacre of some 5,000 Kurds in Halabja in 1988 and the Tokyo subway attack by the cult Aum Shinrikyo in 1995.

VX was prepared in the early 1950s in the United Kingdom, again during a search for new insecticides. It was found to be far more toxic than sarin and too dangerous to be used as an insecticide.

Older readers may remember that VX was the agent that killed some 6,000 sheep in Skull Valley, west of Salt Lake City, in 1968 during a U.S. Army aerial test involving a faulty spray tank.

More recently, VX was used to assassinate Kim Jong Nam, the half brother of the North Korean dictator Kim Jong Un, widely seen on television. Also in the news recently were the new Russian agents called “novichoks,” developed in the 1970s and 1980s, but about which little is known.

Why are nerve agents so toxic? These incredibly lethal chemicals affect — essentially kill — the nerve-associated enzyme acetylcholinesterase, causing respiratory failure and death.

This life-essential enzyme, which is present in all animals and resides in nervous and muscle tissue and in red blood cells, is the fastest acting (most efficient) enzyme known. It is inhibited (destroyed) by minuscule amounts of nerve agent causing death if untreated.

Other consequences of nerve gas exposure are pupil constriction (often the first noticeable effect as communicated to me by Dr. Schrader), slowing of the heartbeat, increased salivation and sweating, vomiting, involuntary urination and defecation, severe muscle cramps, convulsions, headaches and hallucinations.

Unlike some of the other chemical weapons, nerve agents have no effect on the skin and little or no odor, although I have heard that VX smells like bubble gum.

As Gen. John J Pershing said at the end of World War I, “Whether or not gas will be employed in future wars is a matter of conjecture, but the effect is so deadly to the unprepared that we can never afford to neglect the question.”

Will the specter of chemical warfare ever go away? Let us hope.

Gordon W. Gribble, of Lebanon, is an emeritus professor of chemistry at Dartmouth College.