how much more danger was artillery to soldiers in WW1 as opposed to 1870
Well, that question is far more than one of range - the full answer lies in different tactics. I wrote the following to be part of a website on WWI artillery that I have in mind - should I ever make the time:
"Feld-Artillerie tactics prior to the war emphasized following the infantry and then moving the batteries quickly into position to engage the enemy at short ranges, firing over open sights. This tactic frequently was demonstrated with cavalry-like panache during the Kaiser's annual maneuvers. Observed fire was the standard target-attack method, with the battery commander himself usually performing as the observer. The development of indirect fire methods began in the years just before the outbreak of the war and as the war progressed, trench warfare would demand different Artillery tactics, including the utilization of forward observers and a gradual shift to predicted fire or map-based target-attack techniques. During the early days of the war, the Fuss-Artillerie supplanted the Feld-Artillerie as the decisive fire support arm due to its success in defeating the border fortresses and because high-angle fire was essential for trench warfare. Heavy Artillery was also critical for preparations prior to attacks, particularly for attacking deep targets in the enemy's rear and for counterfire against enemy artillery. Initially, Artillery preparations were massive affairs, sometimes lasting days, followed by a technique known as creeping fire, shifting forward just ahead of the infantry advance. Predicted fire allowed a German Artillery officer, Colonel Georg Bruchmüller, nicknamed Durchbruchmüller (a play on his name and the German word “durchbruch” meaning breakthrough) to develop the concept of a centrally-controlled surprise massive bombardment just prior to the infantry attack. This successful innovation replaced the concept of creeping barrages even with the Allies."
Of course, just the volume of ammunition expended during WWI as compared to 1870 made life pretty dangerous. Add the idea of constant harrassing fire - along with your initial thought of range - reaching far behind the lines with larger caliber weapons, as well as artillery-delivered gas attacks, and there should be no doubt that artillery was much more dangerous in WWI than in 1870. I've read somewhere that 60% of all casualties in WWI were the result of artillery. I'd have to go and search my references to give you an authoritative source on that statistic if you desire.