Bassam Khabieh/Reuters

Mass graves for the hundreds of civilians who died in sarin attacks on the Syrian town of Zamalka in eastern Ghouta in August 2013. After the attacks the Syrian government, under the threat of US military retaliation, agreed to the elimination of its chemical weapons but was able to keep its stockpiles of chlorine, which it has reportedly used in attacks on civilians.

Chlorine, which is widely used for water purification, sanitation, and the manufacture of modern medicines, is essential for human well-being in today’s world. As epidemics of waterborne diseases escalate across Syria in besieged and opposition-held areas, the Syrian government’s systematic withholding of the primary means to decontaminate water in these areas can be considered an indirect weapon of mass destruction. However, although minute quantities of chlorine are life-saving, if too much is inhaled in its gaseous form, it can cause death in under thirty minutes. Recently, the Syrian government has used chlorine directly against civilians as a chemical weapon. Syrian President Bashar al-Assad has thus transformed a principal element of public health into a tool of both disease and terror.


Good Chlorine

Human life depends on water—clean water. Attempts to purify water are described in ancient Hindu, Sanskrit, and Greek texts, and passing references are even made in the Old Testament.

Yet the means to kill waterborne microbes was lacking until the discovery of pure chlorine in the early nineteenth century. Nowadays, we take a constant supply of safe water for granted, and chlorine has been our principal agent of water purification for well over a century. In the US, it has been mandated to decontaminate drinking water since 1914.

Chlorine, one of the basic elements, was isolated in gaseous form in 1810 by Sir Humphry Davy, and named for its pale green color (khlōros, in ancient Greek). Its ability to decontaminate derives from its oxidizing properties: it rapidly reacts with and inactivates the proteins that hold cells together. In sufficient concentration, it is poisonous to all species of life.1 Chlorine’s potential for industrial sanitation initially went unnoticed because its discovery predated by several decades the germ theory of disease. At that time disease was believed to be caused by miasma: poisonous particles of dead and decaying matter suspended in foul-smelling clouds arising from graves, swamps, and cesspools.

However, the focus on putrid smells as a sign of miasma led to chlorine’s first clinical use. In 1847, Ignác Semmelweis, a Hungarian physician in Vienna, used chlorine to get rid of the stench of death on his hands after handling cadavers before going onto the maternity ward, and he made his residents do likewise. The death rate on his ward plummeted, but his efforts to broadly institute hygienic practices in hospitals were rejected by the medical community, and he was eventually committed to an insane asylum, where he died of overwhelming sepsis two weeks later.

Meanwhile, cholera epidemics had started appearing in the West. Cholera was spread by pilgrims returning from the Ganges, its ancient reservoir; there were six pandemics and millions of deaths. Early outbreaks in London and New York in the 1830s were covered up, but they got the British physician John Snow, known for his discovery of the link between sewage contaminating the water supply and this deadly disease, thinking about germ theory. Fearing the medical community’s antagonism, he proceeded cautiously, calling cholera a “poison,” but he famously convinced officials to remove the handle of the Broad Street water pump during the London cholera epidemic in 1854, which resulted in a decline in the number of cases in the neighborhood. This prepared the way for the redesign of the water supply system and the widespread use of chlorine to disinfect drinking water. Decades later, Pasteur finally proved the relationship between germs and contagious disease.

The practical application of germ theory—pasteurization, sanitation, vaccinations, and antibiotics—forms the basis of modern medicine. Cholera, as well as typhoid—two bacterial diseases that killed more people than all wars put together—were finally brought under control in the developed world by the widespread use of chlorine. In 1900, typhoid alone killed more than 25,000 people in the United States. By 1960, that had dropped to 21.

Mike King

Today 90 percent of water sources in the United States and Europe rely on chlorine for safe water. This is still the most important use of chlorine, and yet so commonplace that we have forgotten its vital role in human well-being. There are other ways to treat water, but chlorine is unique in keeping water pure all the way to the kitchen tap. Bottled water abounds, but in New York City, for example, we don’t think twice about drinking our tap water.

For many of us, when we think of chlorine, we think of bleach. We use it to whiten whites in our laundry, sanitize our kitchens, and disinfect our toilets. In hospitals, it is the industrial killing machine of microbes in operating rooms. In West Africa, it is an essential ally in the ongoing fight to stop the spread of Ebola. Chlorination inactivates the germs in phlegm and other bodily fluids that tend to seep into pool water, protecting us from colds, flu, conjunctivitis, and other diseases.


Beyond public health, chlorine is fundamental to modern medicine. Chlorine compounds form the building blocks for 90 percent of modern drugs: antibiotics and antimalarials, asthma drugs and antihistamines, chemotherapeutic agents and cholesterol-lowering agents, anesthetics, common pain-relieving agents like Tylenol, and anxiety-reducing drugs such as Xanax, to name a few. John Snow is also celebrated for his anesthetic expertise: he safely used chloroform, a chlorine compound, for the delivery of two of Queen Victoria’s children. PVC, an acronym so common we have to pause to remember what it stands for (polyvinyl chloride), is used in the manufacture of 85 percent of medical devices: not just sterile gloves, dialysis tubing, urinary catheters, and bags for intravenous fluids, but also X-ray films, prosthetics, prescription glasses, and now Ebola protection suits.

But the importance of chlorine in public health in the developed world has no counterpart elsewhere. Louis Pasteur once stated, “80 percent of diseases are in what we drink.” More than one hundred years later, little has changed. Polio, cholera, typhoid, and other waterborne diseases are still major concerns in the developing world.

Recognition of Pasteur’s truth was reflected by the UN Committee on Economic, Social and Cultural Rights in 2000 when it cited clean water and sanitation as crucial determinants of the right to health—a connection reiterated in the Millennium Development Goals.2 In 2012, the World Health Organization (WHO) reported that unsafe water supplies, sanitation, and hygiene are still responsible for the deaths of nearly one million people annually. Haiti’s cholera epidemic in 2010, brought in by UN peacekeepers from Nepal, compounded the country’s widespread misery, causing nearly 700,000 cases and upward of 8,540 deaths at last count. The UN declared itself immune from any accountability.


Bad Chlorine

Though barely recognizable after four years of one of the worst conflicts since World War II, Syria used to be a middle-income country. For decades, chlorine was routinely used for safe water, sanitation, and the manufacture of medicines for both domestic consumption and export. But for several years before the beginning of the popular uprising in March 2011, and in part contributing to it, the Syrian government denied many public health measures to areas of the country that were politically unsympathetic to it, selectively withholding not only chlorine for treatment of water contaminated by sewage, but also routine childhood vaccinations. That continues today, with widespread denial of chlorine to Deir Ezzor, Raqqa, Daraa, the outskirts of Damascus, and other areas outside government control. A few drops of bleach would be sufficient to disinfect water and hands, but it is simply unattainable. In besieged areas, such as Ghouta, water is frequently cut off altogether as a punitive measure.

The consequences of this deprivation are magnified by mass displacement, with ten million civilians having been forced to flee their homes, often leaving three or four families together in households of appalling and unhygienic conditions. 642,000 Syrians live under siege, in even worse conditions. Myiasis—a maggot-ridden wound infection associated with lack of water—appeared in Ghouta last year, at the same time as a water cutoff. In Deir Ezzor, untreated tap water comes directly from the Euphrates River, two hundred yards downstream from a sewage pipe. As a result, there were more than 30,000 cases of hepatitis A across the country in 2014, with several fatalities in young children. This disease is rarely seen in the US, and hardly ever in fatal form.

On February 24 of this year, WHO issued an alert on the risk of cholera in Syria, a concern heightened by the sudden outbreak in Hama in mid-March of more than five hundred cases of acute watery diarrhea. The combination of inadequate surveillance, the absence of laboratories to test for cholera, and previous cover-ups by the Syrian Ministry of Health of cholera in 2005 and 2009 and polio in 2013 suggests that cholera may indeed be back. Even my colleagues in Damascus, where most water is still chlorinated, have suffered from hepatitis; others have succumbed to typhoid. Typhoid is now endemic in southeastern Deir Ezzor—the same area where polio first reappeared in 2013.

The governorate of Daraa has just reported more than two hundred cases of hand, foot, and mouth disease, which spreads easily to children exposed to unchlorinated water that has been contaminated by the stool of an infected child. Scabies and lice are everywhere. Many other water-related diseases, such as polio, giardia, schistosomiasis, and Legionella, are difficult to diagnose and treat without specialist doctors, well-equipped health facilities to collect blood, stool, skin, and urine samples, and labs for isolation of the pathogen—most of which the Syrian government has destroyed in opposition-held areas.


Polio, the most devastating disease of childhood, might never have reemerged in Syria if chlorine had still been available. The polio virus is extremely hard to kill, and chlorine is one of the few agents capable of destroying it. It did not reappear in neighboring Iraq despite eight years of war with inconsistent vaccination but consistent use of chlorine. In Syria, however, the withholding of polio vaccine was compounded by the lack of safe water and sewage treatment, and this horrific disease reappeared after less than two years of war.

Moreover, infection of pregnant women is once again commonplace, as are postoperative wound infections. The destruction of the pharmaceutical industry in Aleppo in 2012—as part of the government’s systematic assault on health care in opposition-held areas—means that there are no longer the means to produce antibiotics like Cefaclor, commonly used for chest and ear infections, or antiseptics like chlorhexidine, a routine scrub for surgery. Recently, of four cases of confirmed malaria, one man died due to lack of chloroquine, a chlorine-based compound.


Deadly Chlorine

Having made civilians in opposition-held areas suffer from the lack of chlorine, the Syrian government is now, in a cruel irony, making it suffer from too much chlorine—in the form of chemical weapons. The chemical massacre in eastern Ghouta in August 2013, which used missiles loaded with sarin, killed some 1,400 civilians. In a deal negotiated by Washington and Moscow under the threat of military retaliation, the Syrian government was forced to give up a sizable part of its chemical arsenal, including 581 tons of the precursors of sarin and twenty tons of ready-to-use sulfur mustard.

However, because chlorine has legitimate uses, the government was not required to eliminate its chlorine stockpiles. Since then, Assad has periodically used chlorine as a chemical weapon—even though such use violates the Convention on Chemical Weapons, which Syria has ratified.

If chlorine is not heavily diluted, inhaling it in its gaseous form causes choking and can be fatal. According to the UN Human Rights Council’s Commission of Inquiry for Syria and an Organization for the Prohibition of Chemical Weapons (OPCW) report of September 10, 2014, chlorine was repeatedly used in this way as a weapon in the Syrian villages of Talmenes, Al Tamanah, and Kafr Zita in April 2014.

The reports of the OPCW and Commission of Inquiry include evidence collected by my colleagues Dr. Khaled Almilaji and Hazem Alhalabi, members of the Chemical Biological Response Network (CBRN) Task Force, which obtained the forensic samples proving that chlorine had been used as a weapon in Syria. In April 2014 alone, there were ten attacks in which chlorine was dropped on civilians in villages in northern Syria, killing eight and affecting almost nine hundred. All but one of the attacks occurred at night and involved the aerial dropping of barrels of compressed chlorine gas, which spread when they hit their target.

Only the Syrian government forces have helicopters that can carry out such bombing. Chlorine gas is not nearly as deadly as mustard gas, which killed more than 90,000 in the trenches of World War I—but it is extremely cheap, does not require the sophisticated missiles needed to deliver sarin, and is highly effective as a weapon of terror. As one Syrian doctor told me:

We are used to the density of bloodshed. To damaged and mutilated people…. But the fear and suffering that these attacks create is unbearable, even for us.

Victims of chemical attacks must be washed, decontaminated, and ventilated, and this should be done out in the open where the water can be drained and the gas can be dispersed. Yet because of the Syrian government’s systemic attacks on the doctors and hospitals in opposition-held areas, all the remaining functioning hospitals there are now literally underground. That makes the dispersal of gas and the drainage of water slow and difficult, endangering medical staff. The Talmenes attack on April 21, 2014, occurred while I was teaching Syrian doctors on the Turkish border. One of my colleagues helped treat the hundreds of patients, several of whom died:

I was on the ground with the patients, washing them. Of course, we knew we were also in danger, but could not even begin to take care of ourselves when faced with so much suffering. And what was there to change into? We had half a dozen pairs of gloves between us. No protective suits. I’m still wearing the same suit. My eyes and hands hurt, but I’m ok.

On March 6, 2015, the UN Security Council condemned the use of chlorine as a chemical weapon, though at Russia’s insistence the council didn’t name the Syrian government as the perpetrator or impose any sanctions.

And yet ten days later, I watched videos sent by my Syrian colleagues showing dying and newly dead children, unbearably vulnerable to the chlorine dropped on them. After the first chlorine bomb went off at 8:30 PM, one entire family—three very young children, their parents, and their grandmother—took cover in a basement, knowing there would likely be a second bomb. The lights literally have gone out in most of Syria, so it was pitch-black in Sarmin, a village in the northwestern governorate of Idlib, where the attack occurred. No one could see the yellow gas, but they could smell it. The second bomb struck their house, trapping them inside, where they would suffer increasing difficulty breathing and ultimately suffocate to death. Dr. Muhammad Tennari described the chaos:

The children came in their sleeping suits. The grandmother was dead on arrival but there was nowhere for her body. We had to place two of the children on top of her body, trying to resuscitate them…. We barely had water to wash patients, let alone oxygen or life-saving ventilators. No clothes for the children, left naked. And other casualties kept on coming.

Journalists questioned my colleagues: “Did you hear any strange sounds? Did you smell anything strange? Why didn’t you see any yellow gas, if it was chlorine? And isn’t atropine used for sarin, not chlorine?” Dr. Almilaji replied:

It was nighttime, no one can see anything. We hear rockets all the time. There are months when shelling happens twenty-four hours a day, seven days a week. We hear snipers. Missiles. Drones. Long-range cannons. Al-Assad’s arsenal has many different sounds, we know them all. As for atropine, if it is a chemical attack, we give atropine, period. The same emergency drugs are always given in chemical attacks—oxygen, atropine, salbutamol, hydrocortisone even in the best functioning hospitals in Aleppo, let alone field hospitals in rural Idlib. But there is no antidote for chlorine, a choking agent. We are not taught about chemical weapons in medical school. We may not know what we are dealing with, and can only give the drugs that we have.

Since March 10, worried about ISIS attacks emanating from Syria, Turkey has closed its borders, increasing the difficulty for Syrian doctors trying to bring out samples to prove that chlorine attacks had taken place. But even without laboratory proof, the smell and effects of chlorine leave no question that this was a chemical attack. Assad has repeatedly denied the use of chlorine, citing as proof the absence of forensic samples that can be delivered for analysis in laboratories. This defense echoes the government’s cover-up of the reemergence of polio by saying it wasn’t proven in a lab. In the nights after March 16, including during my time on the Syrian border at the end of the month, there were some two dozen additional chemical attacks consistent with either pure chlorine or a chlorine cocktail, with hundreds affected, mostly women and children.

The March 16 attack on Sarmin was part of intensified fighting around Idlib, which fell to opposition forces on March 28. Tens of thousands of civilians have fled but are unable to reach the safety of Turkey and thus remain vulnerable to the government’s retaliation. Humanitarian aid is still allowed in, but many agencies backed by Western governments have joined the Syrian government in blocking the delivery of chlorine to protect public health in ISIS-controlled territory. Surgeons are denied minute amounts of this most basic tool of preventive health out of fear that the few pints used to disinfect operating rooms will be seized by ISIS to make chemical weapons. Yet for two years now, ISIS has repeatedly allowed the safe passage of not only disinfecting agents but also millions of liters of pesticides to combat the spread of leishmaniasis in Aleppo and Idlib.

For four years, the Assad government has been treating Syrian doctors in opposition-held areas as terrorists, penalizing, incarcerating, and executing them for providing care to anyone in need. To add insult to injury, Western aid agencies and donor governments are now compounding the problem by denying them basic tools of public health out of a singular and often exaggerated preoccupation with ISIS.

However, sending atropine, a drug often used for emergency resuscitation, is still allowed, which now verges on the obscene to many doctors. As Dr. Majed, who worked on the front lines of the chemical massacre in eastern Ghouta, said to me recently:

The message the Syrians are getting [from Western governments] when atropine arrives is, “We know your government is going to kill your children in the most depraved way possible—and we are not going to stop him [Assad], but we will be able to say we responded.”

At the very least, Turkey should reopen its borders for the safe passage of refugees, doctors, and patients—and to enable proof of chlorine’s use as a chemical weapon. The closure of the borders is not only devastating for the people of Syria; it is also shortsighted for the people of the surrounding region. Microbes need neither permission nor passports.

Clean water goes a long way toward controlling polio, cholera, typhoid, and diarrheal disease of all kinds. Misuse of the tools of public health, and loss of control of these highly contagious diseases, have regional and global repercussions.

As for the use of chlorine as a chemical weapon, it needs more than general condemnation without consequences by a Security Council in paralysis. There is yet more life than death in Syria—eight hundred babies are born each month in Ghouta alone. The youngest children always suffer the worst of war—from the disease, the destruction, the degradation and insecurity. They deserve protection from an inhumane regime that has delivered diseases from the Dark Ages and repeatedly targeted civilians with deadly weapons without any meaningful international response. The international community is now preoccupied by the threat of ISIS, but the people of opposition-held Syria will not provide their essential support to anti-ISIS efforts if the world continues to ignore the greater slaughter, disease, and deprivation caused by the Syrian government.

—April 2, 2015