Supreme Court upholds HC ban on plaster of Paris Ganesh idols

Subject :Environment

Section: Pollution

Context:

There have been efforts to ban the sale of plaster of Paris (PoP) idols for Ganesh Chaturthi festival in the past, but these have proved futile.
NGT has ordered state pollution control boards to constitute expert committees to study the impact of PoP on water bodies.

Details:

There is no definitive and comprehensive scientific study on the impact of PoP on the environment.
Studies have been carried out in some places like Bhopal, Jabalpur and Bengaluru. Results find the impacts including steep rise in concentration of heavy metals, dissolved solids, and acid content, and a drop in dissolved oxygen.

Plaster of Paris (POP):

PoP is made by heating gypsum at temperatures in the range of 300°F.
When it comes in contact with water, the material regains the form of gypsum.
Since gypsum is a naturally occurring substance, and is used as a soil-conditioner to reclaim saline-sodic soils, it has been argued by idol-makers’ associations that it is harmless to the environment.

Properties of Plaster of Paris:

Usually white in color and available in powder form.
When water is added, gypsum crystals are formed, leading it to achieve a solid state.
The exothermic setting process can be catalyzed by sodium chloride. The plaster of Paris is retarded by alum or borax.
Plaster of Paris forms anhydrous calcium sulfate at 473 K. This is sometimes known as the dead burnt plaster of Paris.

Impact of POP idol immersion:

Some other activists argue that PoP idols are non-biodegradable.
PoP’s reaction with water is exothermic—it releases heat when in contact with water. There are no studies on what kind of impact the heat thus generated has on aquatic life in water bodies.
PoP idol immersion makes the water cloudy.
The idol is painted with oil paint. Common pigment types in those oil paints include mineral salts such as white oxides: zinc oxide, titanium dioxide, and the red to yellow cadmium pigments.Paints used for colouring the idols consist of various heavy metals pigments such as white lead, lithopone, chrome yellow, cadmium sulphide, barium chromate, vermillion, red lead etc.
Chemicals used in the idols are also harmful for the aquatic environment. They contain heavy metals like lead, mercury, copper and cadmium.
Adding large quantities of gypsum to water will raise its hardness and reduce its life-carrying capacity.
It flows into landfills and unused quarries around the cities.
Many aquatic animals die because of overload of bacteria resulting from the immersed flowers and sweets given as offerings.