In 2016, one in four civilian deaths in the Syrian war were children, according to new estimates published in The Lancet Global Health journal. The study finds that since 2011, the conflict has claimed the lives of an increasing proportion of children as a result of the systematic use of aerial bombing on populated areas, which disproportionately affect civilian women and children.
The study uses data on deaths in non-government-controlled areas documented by the Violence Documentation Center (VDC), an independent group with a ground network of 30-35 investigators in Syria covering each province. 
"Our findings underscore the highly limited efficacy of shelling and aerial bombing against opposition fighters, and the disproportionate lethal impact on civilians, particularly children. These findings call into question the use of these weapons in populated urban areas and suggest possible indiscriminate weapons use contrary to international humanitarian law." says lead author Professor Debarati Guha-Sapir, Université catholique de Louvain, Belgium. 
In the first six years of conflict, 70.6% of the deaths documented as part of the study were civilians (101453/143630), and 29.4% were opposition fighters (42177/143630). The majority of civilian deaths have been men (71.9%, 72940 men), followed by children (17.2%, 17401 children) and women (11%, 11112 women). Because government-controlled areas are unsafe for the VDC staff to enter, the study does not include data from these areas. While the study provides evidence of trends in violent events recorded by VDC, it does not represent the total impact of the conflict.
The Syrian conflict started as peaceful demonstrations in March 2011, but, in June 2011, escalated into an armed rebellion against President Bashar Al-Assad and his government including anti-government groups such as Salafi jihadist groups, the Islamic State of Iraq and the Levant (ISIL), Syrian Democratic Forces, and Free Syrian Army. Warring parties in Syria have since expanded to include international groups such as Russia, USA, Iran and Palestine.
According to the Syrian Centre for Policy Research, the war has displaced over half of the Syrian population, and resulted in a drop in life expectancy of up to 20 years by 2014.
In The Lancet Global Health study, the researchers found that, at the outset of the war, shootings caused most civilian deaths, but that shelling became the main cause of death in early 2013. In August 2012, deaths by aerial bombings increased.
Overall, more than half of civilian deaths documented in this study were caused by shelling and aerial bombs (57.3%, 58099/101453), compared to less than one in 10 documented deaths of opposition fighters (9.6%; 4058/42171 deaths).
While male civilian deaths were caused equally by shells, shootings, executions and aerial bombing (around 23-26% of deaths were caused by each type of weapon), women and children were mostly killed by shells and aerial bombs (shelling caused 37.7% of deaths of women and 37.3-38.7% for children. Aerial bombing caused 36.9% of deaths of women and 39.2-46.3% for children). This impact has increased as the use of these weapons grew from 2014 when international parties intensified the aerial bombing of Syria.
Based on the provinces the VDC staff were able to access, the greatest numbers of civilian deaths were documented in Homs until late 2012, when deaths in Damascus and Aleppo increased dramatically and saw the highest figures. These two locations have witnessed nearly 25% of all deaths, and the highest proportions of child deaths by shelling. Aleppo was also home to 40% of all child deaths by aerial bombing, a figure twice that of other provinces after a rapid increase in deaths of this kind in 2013.
Barrel bombs caused a very high proportion of civilian deaths, and almost all documented deaths from barrel bombs included in the study were civilian (97.2%, 7351/7566 deaths) and a quarter were children (27.3%, 2007/7351) .
Almost three-quarters of barrel bomb deaths (72.4%, 5322 deaths) occurred between January 2014 and June 2015, and almost two-thirds (65.6%, 4820 deaths) occurred in Aleppo.
The authors note that barrel bombs have been dropped on hospitals, markets, and homes, and sometimes used in 'double-tap strikes' where a second barrel bomb is dropped minutes after the first in an attempt to eliminate first responders and medical services. In March 2017, The Lancet published the first report from its Commission on Syria highlighting how health care was being used as a weapon of war in Syria. 
Professor Guha-Sapir notes: "Among the explosive weapons used, the vast impact of barrel bombs on civilians compared with their lesser effect on opposition fighters shows an extreme disparity. This supports claims that barrel bombs may have been used to directly target civilians, or that barrel bombs constitute an indiscriminate weapon. Approximately three quarters of recorded incidents of explosive weapon use in Syria have occurred in densely populated civilian areas, putting civilians at very high risk and suggesting a degree of intentionality." 
The authors note that due to changes in intensity of the conflict, control of areas, blocked access or threats to VDC staff, data collection varied of over time and location. The number of deaths caused by wide-area explosive weapons is likely to be underestimated due to loss of bodies in these events, however they note this is unlikely to affect the finding that these weapons disproportionately kill civilians.
The study does not include deaths caused indirectly by war (such as increased disease, severe shortages of medical staff and supplies, and reduced access to medical facilities) or deaths of people who have fled the country, been detained or disappeared.
Writing in a linked Comment, Dr Hani Mowafi, Yale University, USA, says: "The Syrian civil war, now in its 7th year, has inflicted a grave toll on the country's population and public health system. The conflict has destroyed Syria's public health infrastructure, inflicted marked excess direct and indirect mortality, and forced widespread displacement of more than half of the Syrian population... Documentation of the health impact of war and conflict is one of the most difficult yet important public health challenges. An essential effort is to arrive at a robust estimate of who has been killed and injured, by what means, over the duration of hostilities. Countries that descend into conflict frequently have inadequate vital statistics systems and woefully incomplete death registries prior to that descent. Wars further vitiate any attempt at accounting. Yet, the health and population impact of conflicts is dramatic and their effects long lasting. Any attempt to understand these events requires careful data collection and contemporaneous analysis to capture data that would otherwise be lost."
NOTES TO EDITORS
This study received no funding. It was conducted by researchers from Université catholique de Louvain, Centre on Global Health Security, and University of Massachusetts Medical School.
 The VDC aim to collect data on all violent deaths in the region, including demographic, date of death, location, cause of death, and whether they were a civilian or fighter.
 Quote direct from author and cannot be found in the text of the Article.
 Barrel bombs comprise of barrels or cylinders filled with explosives, shrapnel, nails, and oil, which are dropped from helicopters or planes and fragment on impact with a large blast radius capable of decimating a city block.
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