Indian Express Explained 28th April 2020

Print Friendly, PDF & Email

1)Explained: What are human challenge trials, and why are they controversial?

How are vaccines usually developed?

In most regulatory regimes, vaccines take several years to develop, and their development typically proceeds through three phases of clinical trials.

In Phase 1, small groups of people receive the trial vaccine.

During Phase 2, the clinical study is expanded and the vaccine is given to people who have characteristics (such as age and physical health) similar to those for whom the new vaccine is intended.

In Phase 3, the vaccine is given to several thousand people and tested for efficacy and safety.

Duringthis phase, participants either receive the vaccine or a placebo. The efficacy of the vaccine is determined by comparing the prevalence of infection in the group that was administered the vaccine with the one which received a placebo.

What are human challenge trials?

Under human challenge trials, participants of both the vaccine group and placebo group upon consent are deliberately exposed to the infection – thus are “challenged” by the disease organism.

Human challenge trials: The ethical concerns

While human challenge trials are not new, they are usually carried out in developing medications for diseases which are considered less lethal and have been better understood by scientists over the years, such as malaria.

Critics have questioned undertaking such trials for Covid-19, a potentially deadly disease for even those who are less at risk, and which researchers are still in the early stages of studying.

Proponents of the method believe that such trials could save valuable time in developing a Covid-19 vaccine, as researchers would not have to wait for participants to contract the infection under real-world conditions.

2)Explained: How the ozone layer hole over Arctic closed

The ozone hole’s closing was because of a phenomenon called the polar vortex, and not because of reduced pollution levels due to Covid-19 lockdowns around the world, reports said.

The importance of the ozone layer

Ozone (chemically, a molecule of three oxygen atoms) is found mainly in the upper atmosphere, an area called the stratosphere, between 10 and 50 km from the earth’s surface. Though it is talked of as a layer, ozone is present in the atmosphere in rather low concentrations. Even at places where this layer is thickest, there are not more than a few molecules of ozone for every million air molecules.

But they perform a very important function. By absorbing the harmful ultraviolet radiations from the sun, the ozone molecules eliminate a big threat to life forms on earth. UV rays can cause skin cancer and other diseases and deformities in plants and animals.

The ‘ozone hole’ is not really a hole — it refers to a region in the stratosphere where the concentration of ozone becomes extremely low in certain months.

Why this year’s Arctic ozone hole was massive

This year, the ozone depletion over the Arctic was much larger. Scientists believe that unusual atmospheric conditions, including freezing temperatures in the stratosphere, were responsible.

What is Polar Vortex:- The polar vortex is a large area of low pressure and cold air surrounding both of the Earth’s poles. It ALWAYS exists near the poles, but weakens in summer and strengthens in winter. The term “vortex” refers to the counter-clockwise flow of air that helps keep the colder air near the Poles.

3) Soil Health Card :- Soil Health card (SHC) is a printed report card issued to farmers in once in three years indicating the status of his soil in terms of 12 parameters. It is also accompanied by an advice on the various fertilizers and other soil amendments he is suppose to make.

SHC is field-specific detailed report of soil fertility status and other important soil parameters that affect crop productivity. Details in a Soil Health Card includes

  • Information regarding Soil Fertility
  • Dosage of fertilizer application in crops.
  • Information on soil amendments of saline or alkaline soil; and
  • Recommendation on integrated nutrient management.

The 12 parameters tested are:

Major Nutrients

  • pH (Soil Reaction; acidity / alkalinity of the soil)
  • Total Dissolved salts
  • Organic Carbon
  • Phosphorous
  • Potash

Minor Nutrients

  • Sulphur
  • Magnesium
  • Calcium


  • Zinc
  • Ferrous
  • Manganese
  • Copper

The Test Results are shown with colour codes for ease of understanding.

Green= Sufficient (General Recommendation Dose (-) 30%)

Yellow= Moderate (General Recommendation Dose)

Red = deficient (General Recommendation Dose (+) 30%)

Violet = Acidic / Sodic (concentration of sodium or salt indicating salinity) /Alkaline

The issue of Soil Health Card was taken up in a mission mode format in February 2015. Every farmer in the country is proposed to be issued the SHC.  14 crore Soil Health Cards are envisaged to be issued over the next 3 years[1].

Benefits of SHC
The existing Nitrogen – Phosphorous – Potassium (NPK) consumption ratio in the country is skewed at 8.2:3.2:1 (2012-13) as against the preferred ratio of 4:2:1.

A great variability is observed in fertiliser consumption among States from 250 kg / hectare (ha) in Punjab, 212 kg / ha in Bihar, 207 kg / ha in Haryana to 4.8 kg / ha in Nagaland and 2 kg / ha in Arunachal Pradesh, during 2012-13. However, imbalanced application of fertilisers have caused deficiency of primary nutrients (i.e. NPK), secondary nutrients (such as sulphur), and micronutrients (boron, zinc, copper etc.), in most parts of country.

SHC will ensure that farmers do not spend money unnecessarily on purchase of fertilizers by adding more than required.  Once there is economy on the use of chemical fertilizers, the cost of production is expected to decrease.  Promotion of integrated nutrient system is expected to reduce the consumption of chemical fertilizers by 20% thereby easing the fiscal strain on Government.

Fertiliser sector accounts for a significant percentage of the total subsidies and power consumption in the country. India imports large quantity of various fertilizers to meet the demand. About 25-30% of the requirement of Urea, 90% of the requirement of Diammonium phosphate (DAP) and 100% of the requirement of Muriate of Potash (MOP) are met by imports. The soil test based fertilizer usage will reduce import bill and will also ensure higher yields per unit.

Over a period of time SHC can determine changes in soil health that are affected by land management.


One thought on “Indian Express Explained 28th April 2020

Leave a Reply

%d bloggers like this: