Premium

UPSC Weekly Concepts Snapshot: Qdenga, Principal Purpose Test and POPs explained

Can one vaccine protect against all four dengue virus strains? How do countries prevent tax treaty abuse? And why are Persistent Organic Pollutants a global environmental concern? Here's all you need to know.

UPSC Weekly Concepts Snapshot: India’s first dengue vaccine, Principal Purpose Test, Persistent Organic PollutantsHere are three important topics from Science, Economy, and Environment decoded focusing on concepts and clarity. (Image: AI generated)
Written by: Roshni Yadav
10 min readNew DelhiJul 26, 2026 11:15 AM IST First published on: Jul 22, 2026 at 10:29 AM IST

Headlines tell you what happened, but UPSC asks why. The UPSC Civil Services Examination, whether at the Prelims or Mains stage, increasingly rewards conceptual clarity and the ability to apply core ideas. That is especially true in the most dynamic areas of the syllabus: Science, Economy and Environment. 

The UPSC Weekly Concepts Snapshot, every Wednesday, simplifies three important current themes from these subjects through an exam-oriented lens, focusing on concepts and clarity. 

Advertisement

If you missed the previous UPSC Weekly Concepts Snapshot | ‘One-click’ exploits, Agriphotovoltaics, Total Solar Eclipse explained from the Indian Express, read it here.

SCIENCE

India’s first dengue vaccine

Why it matters

The Drug Controller General of India (DCGI) has approved Japanese company Takeda Biopharmaceuticals India’s dengue vaccine, Qdenga, making it the first such vaccine to be greenlighted in India. The approval comes at a critical time for public health, with reported dengue cases in India increasing 11-fold over the past two decades. In this context, let’s know about the Dengue and Qdenga.

Core Concept:

— India continues to account for nearly one-third of the global dengue burden. Dengue is a mosquito-borne viral disease that poses a significant global public health threat, with prevalence in over 125 countries. 

📍UPSC Twist Points: Zika Virus

— A mosquito-borne disease—Zika virus— mainly occurs in tropical and subtropical areas of Africa, the Americas, Southern Asia, and the Western Pacific.

UPSC Weekly Concepts Snapshot: India’s first dengue vaccine, Principal Purpose Test, Persistent Organic Pollutants Here’s how the Zika virus spreads (Source: CDC)

— It is infected by Aedes species mosquitoes, which are the same ones that spread dengue and chikungunya viruses, and bite during the first week of infection. It is primarily transmitted through mosquito bites, sex, and breastfeeding.

Q1. Consider the following statements: (UPSC CSE 2017)

1. In tropical regions, Zika virus disease is transmitted by the same mosquito that transmits dengue.

2. Sexual transmission of Zika virus disease is possible.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

ECONOMY

Principal Purpose Test

Why it matters 

India has amended its tax treaty with Sri Lanka to tighten loopholes in double taxation avoidance and to curb revenue leakage by preventing treaty abuse. The intention for amending the pact has been to eliminate double taxation without creating opportunities for non-taxation or reduced taxation through tax evasion or avoidance through treaty-shopping arrangements. The amended treaty between the two countries has included the Principal Purpose Test (PPT). In this context, let’s know what PPT is.

Core Concept:

— An anti-avoidance tool, the PPT ensures denial of benefits under a double taxation avoidance agreement (DTAA), where it is reasonable to conclude that one of the principal purposes of an arrangement or transaction was to obtain a benefit, directly or indirectly, under a treaty unless the granting of the benefit was in accordance with the object and purpose of the treaty. 

— The PPT is intended to ensure that DTAAs apply in accordance with the objects and purpose for which they were entered into, that is, to provide benefits in respect of bona fide exchange of goods and services, and movement of capital and persons.

— Tax authorities will now be empowered to examine the commercial intent behind an investment structure and deny treaty benefits if obtaining a tax advantage is considered one of its principal purposes, unless the arrangement is consistent with the treaty’s object and purpose.

Do you Know?

The ‘Multilateral Convention to implement tax treaty related provisions to prevent Base Erosion and Profit Shifting’ (MLI) entered into force for India on October 1, 2019 

📍UPSC Twist Points: Base erosion and profit shifting

— According to the official website of OECD, domestic tax base erosion and profit shifting (BEPS) relates to tax planning strategies of multinational enterprises that exploit the loopholes in tax rules to artificially shift profits to low or no-tax locations as a way to avoid paying tax.

— The OECD/G20 BEPS Project equips governments with rules and instruments to address these issues of tax avoidance by ensuring that profits are taxed where economic activities generating them take place and where value is created.

Q2. Consider the following statements with reference to the Principal Purpose Test:

1. It allows tax authorities to deny treaty benefits if obtaining a tax advantage is one of the principal purposes of an arrangement or transaction.

2. It seeks to ensure that double taxation avoidance agreement are used only for genuine economic activities consistent with the object and purpose of the treaty.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

ENVIRONMENT

Persistent Organic Pollutants

Why it matters 

The UN Environment Programme (UNEP) and the Global Environment Facility (GEF) have officially launched the US$ 23.5 million Global Chemicals Monitoring Programme (GCMP), intended to help evaluate the effectiveness of the Stockholm Convention on Persistent Organic Pollutants (POPs) and the Minamata Convention on Mercury. In this context, let’s know about the POPs.

Core Concept:

— Persistent Organic Pollutants (POPs) are hazardous, carbon-based manmade chemical molecules that resist environmental degradation, accumulate in the food chain, and travel long distances across international borders, endangering human health and ecosystems. 

— According to Stockholm Convention, POPs possess a particular combination of physical and chemical properties such that, once released into the environment, they:

• remain intact for exceptionally long periods of time (many years);

• become widely distributed throughout the environment as a result of natural processes involving soil, water and, most notably, air;

• accumulate in the living organisms including humans, and are found at higher concentrations at higher levels in the food chain; and

• are toxic to both humans and wildlife.

— As a result of releases to the environment over the past several decades due especially to human activities, POPs are now widely distributed over large regions. 

— The effects of POPs include cancer, allergies and hypersensitivity, damage to the central and peripheral nervous systems, reproductive disorders, and disruption of the immune system. 

Do you Know?

POPs also concentrate in living organisms through another process called bioaccumulation. Fish, predatory birds, mammals, and humans are high up in the food chain and so absorb the greatest concentrations. When they travel, the POPs travel with them. 

— Some POPs are also considered to be endocrine disrupters, which, by altering the hormonal system, can damage the reproductive and immune systems of exposed individuals as well as their offspring; they can also have developmental and carcinogenic effects.

— According to World Health Organization (WHO) “The most commonly encountered POPs are organochlorine pesticides, such as DDT, industrial chemicals, polychlorinated biphenyls (PCB) as well as unintentional by-products of many industrial processes, especially polychlorinated dibenzo-p-dioxins (PCDD) and dibenzofurans (PCDF), commonly known as dioxins.”

📍UPSC Twist Points: PM 1 particles

— PM 1 are extremely fine particulate matter (PM) particles of diameter less than 1 micron — significantly smaller than PM 2.5 (of diameter 2.5 microns).

— These particles, byproducts of emissions from factories, vehicular pollution, construction activities and road dust, are not dispersed, and stay suspended in the air that we breathe. 1 micron is about a thousandth of a millimetre.

Q3. Consider the following statements with reference to Persistent Organic Pollutants (POPs):

1. They resist environmental degradation and accumulate in living organisms.

2. They are naturally occurring compounds that rapidly break down in the environment, preventing biomagnification.

Which of the statements given above is/are correct?

(a) 1 only

(b) 2 only

(c) Both 1 and 2

(d) Neither 1 nor 2

Answer Key

1. (c)  2. (c) 3. (a) 

🚨 Click Here to read the UPSC Essentials magazine for July 2026. Subscribe to our UPSC newsletter. Stay updated with the latest UPSC articles by joining our Telegram channel – Indian Express UPSC Hub, and follow us on Instagram and X. 

Roshni Yadav is a Deputy Copy Editor with The Indian Express. At The Indian Express, she writes for ... Read More

Latest Comment
Post Comment
Read Comments