Fallout/pollution as act of war?
<p>Many contemporary weapons deliver substantial secondary and tertiary damage.  For example:</p>

<ol>
<li><p>The <a href="http://nuclearsecrecy.com/nukemap/" rel="nofollow noreferrer">fallout</a> from <a href="http://www.arcgis.com/apps/Time/index.html?appid=b8540a8a2500472c8037bdd2a35c4be0" rel="nofollow noreferrer">nuclear detonations</a>.</p></li>
<li><p>The various <a href="https://www.nytimes.com/2016/02/09/us/regulatory-gaps-leave-unsafe-lead-levels-in-water-nationwide.html" rel="nofollow noreferrer">epidemiological</a> and <a href="https://www.epa.gov/sites/production/files/2016-01/documents/appendix_d_eco_thyroid_v_7.1.pdf" rel="nofollow noreferrer">ecotoxicological</a> consequences of perchlorate, i.e., rocket fuel (full disclosure: my dad is a scientist cited in the linked EPA document).</p></li>
<li>The long-term ramifications of napalm in Vietnam, on both the <a href="https://www.cancer.org/cancer/cancer-causes/agent-orange-and-cancer.html" rel="nofollow noreferrer">soldiers who used it</a> and the <a href="https://www.theguardian.com/world/2003/mar/29/usa.adrianlevy" rel="nofollow noreferrer">environment and people</a> of that country.</li>
</ol>

<p>What I am curious about is a situation in which these secondary and tertiary ramifications effect some unrelated third party.  For instance, maybe some wind blows a bunch of radioactive fallout-dust from country <code>B</code> which just got bombed over to neutral country <code>A</code>.  Or maybe the napalm dropped on country <code>B</code> poisons the water which flows into country <code>A</code>, and which is the only major water supply for that country.  Etc.</p>

<p>In a situation like this, would the neutral third party have any standing in international law to state that these secondary or tertiary effects constitute an act of war?  Obviously any despot can say "I'm counting this as an act of war" and then wage war, but is there any legal or historical basis to think that international bodies such as the U.N. would generally take the side of the hypothetical country <code>A</code> in such a scenario?</p>

<p>Article 2(4) of the UN charter:</p>

<blockquote>
  <p>All members shall refrain in their international relations from the threat or use of force against the territorial integrity or political independence of any state, or in any other manner inconsistent with the purposes of the United Nations.</p>
</blockquote>

<p>This is generally understood that the only legal <em>casus belli</em> is a response to an armed attack or a UN resolution in support of war. Your circumstances do not meet these criteria.</p>

international laws-of-war environmental