Contaminants and indirect pollution will have a long-term toxic legacy for the environment and can contribute to widespread public health problems for years to come.
Syria's ongoing civil war has already resulted in more than conservative estimates of 120,000 mortalities (including nearly 15,000 children) and has brought enormous destruction in cities and towns all over the country.
Apart from the direct impact of the violent conflict on the lives of Syrian citizens, health and environmental impacts are emerging as serious problems that deserve immediate and long-term attention.
The Syrian civil war is leaving behind a toxic footprint both directly and indirectly resulting from military contamination from all sides.
Public health problems for many years to come
Heavy metals in munitions, toxic residues from artillery and other bombs, the destruction of buildings and water resources, the targeting of industrial zones and the looting of chemical facilities all contribute to long-term negative impacts for communities suffering in war.
The scale of military activity in Syria over the past three years suggests that contaminants and indirect pollution will have a long-term toxic legacy for the environment and can contribute to widespread public health problems for years to come.
Amid prolonged violence, it is too early to assess the full scope of hazards to human and environmental health across Syria formed by toxic or radiological substances that result from munitions and military activities.
However, an early mapping as part of a new study on Syria by Dutch, peace-oriented non-governmental organization PAX reveals a range of problems in certain areas.
Heavy metals and carcinogens
The intense use of large caliber weapons in the prolonged siege of cities such as Homs and Aleppo has dispersed a variety of munitions with known toxic substances.
These include heavy metals, explosive residues from artillery, mortars and home-made weapons containing known carcinogenic materials such as TNT, as well as toxic rocket propellants from a range of missiles launched by both the Syrian army and opposition forces.
The best known examples, the so-called 'barrel bombs', contain hundreds of kilograms of toxic, energetic materials, which often don't explode and could result in local contamination if not properly cleaned-up.
Similarly, the improvised manufacturing of munitions in rebel-held areas involves the handling of a range of toxic chemical mixes, which requires professional expertise and safe working environments mostly absent in the DIY weapons workshops of the Free Syrian Army.
The involvement of children in collecting scrap materials and in production processes poses significant health hazards. Add to this the risk of exposure to pulverized building materials, which may contain asbestos and other pollutants.
Toxic dust particles can be inhaled or ingested as they often end up inside homes, in water resources and on vegetables.
In areas such as the destroyed Old City of Homs, where displaced civilians have begun to return, building rubble and toxic dust from explosives is widespread, exposing the local community and aid workers to potential health hazards.
Furthermore, the absence of waste management in violence-stricken urban areas prevents communities from ridding their neighborhoods of toxic substances that could have a serious impact on their long-term well being.
Makeshift oil production and refining
At the same time, an environmental and public health catastrophe is visibly in the making in Syria's oil-producing regions, where an illegal oil industry is now booming, resulting in unskilled rebels and civilians working with hazardous materials.
Primitive extraction and refining processes by local factions in rebel-held areas are causing the spread of toxic gasses, water and soil pollution in local communities.
Through the smoke and dust that is spread by the unregulated, unclean extraction and refining operations, and leakages that pollute the scarce groundwater in what is traditionally a region of agriculture, the crude refineries' pollution is spreading to surrounding desert villages.
Already, reports from local activists warn of oil-related diseases spreading in Deir ez-Zour. According to a local doctor, "common ailments include persistent coughs and chemical burns that have the potential to lead to tumors."
For the foreseeable future, civilians in the region affected by these problems face serious risks of exposure to toxic gases while vast areas may be becoming unsuitable for agriculture.
Military and industrial sites
Still unclear in this early stage of our research are the potential humanitarian and environmental consequences of the targeting of industrial and military sites and stockpiles.
The Sheikh Najjar industrial city, home to thousands of Internally Displaced Persons from nearby Aleppo, has seen heavy fighting between government and rebel forces.
The risk of civilian exposure to stored toxic substances in such an area is a cause of concern, be it by the targeting of on-site facilities or by refugees being forced to stay in a hazardous environment.
The impact of violent conflict on health and the environment urgently deserves a more prominent role in assessing the long-term consequences of wars.
This should be done both from a military perspective regarding the toxic footprint of certain conventional weapons, and from a post-conflict assessment point of view.
And it must include a far stronger awareness on securing and monitoring health and the environment.
Pieter Both works as a researcher for Dutch non-governmental organization PAX on toxic remnants of war in Syria and holds an M.A. in Conflict Studies and Human Rights. Wim Zwijnenburg works as Program Leader of Security & Disarmament for PAX.