Since we are on this topic,as far as silver iodide, what is its effect on the environment? I have people tell me that is is highly toxic and causes acid rain. What is a good response?
I'm no expert on cloud seeding or silver iodide chemistry, but I did some looking into this back when communicating with the guy from Artificialclouds.com (who thinks that
cloud seeding indirectly causes chemtrails).
First of all, the amount of AgI released is really tiny compared to the area covered. I looked at the
2011 cloud seeding records that agriculturedefensecoalition.org requested from NOAA, and calculated that for those flights where both the amount of AgI and the area covered were reported, they released an average of 3.59 grams per square mile. Studies which have looked at the question (such as
Tsiouris et al. (2002)) have generally found no measurable increase in the soil in areas where cloud seeding is done.
An early review of potential ecological effects is
Cooper and Jolly (1970). They also found that the amount of Ag in rainwater from seeded storms was small, "0.01 to 0.03 g Ag per hectare per centimeter of rain." They found that there were no likely impacts to human health (since even the ingestion of large quantities of silver over a long time only causes tissue discoloration,
argyria). They said that the silver in AgI, if at high enough concentrations, could conceivably have some effects on aquatic microorganisms and fish, but noted that this was based on lab studies using silver compounds such as AgNO3, "which is presumably fully ionized at the concentrations employed." They noted that silver iodide is nearly insoluble. However, they still called for studies which looked more carefully at effects of cloud seeding agents on freshwater systems.
Such studies were carried out as part of a series of projects funded by a program called "Project Skywater," and summarized in
Howell (1977). They found that since the inputs were so small compared to the natural occurrence of silver in the environment and the threshold at which they could have an impact on aquatic life, there was no measurable, direct environmental impact from AgI as used for cloud seeding.
External Quote:
Cloud seeding, if it became widespread, would result in local, temporary concentrations in precipitation of the same order of magnitude as the natural concentrations in surface waters. However, the rates of exchange would remain more than an order of magnitude smaller than the principal exchanges affecting the aquatic compartment, and they would be many orders of magnitude smaller than those affecting plants and soil, even in localized areas of precipitation management. Widespread and prolonged precipitation management, including silver iodide as the cloud-seeding agent and assuming that all the silver dispersed in the course of a century accumulated in the top 2 cm of soil, would not cause the concentration there to exceed the normal background.
They further noted that while environments in some areas were either polluted enough from other sources or naturally enriched enough in silver or to have antimicrobial effects, "Precipitation management activities produce such concentrations only within a few meters of ground-based smoke generators, where some weak evidence of possible delay in decomposition processes is available (Sokol and Klein, 1975). Elsewhere, despite diligent monitoring, no trace of silver attributable to cloud seeding, or impact of such silver, has been found."
So to sum up: it has been studied, and the amount of silver iodide released is tiny compared to the natural amount of silver in the environment. It's generally too small to even cause a detectable increase of silver in soil or surface waters, much less cause measureable effects on the environment or human health. The "causes acid rain" part is a new one on me. Silver iodide has no effect on pH, as far as I know.
