The Green Cracker Paradox: Less Pollution, But At What Cost?

Green crackers are meant to reduce air pollution. But research conducted during Diwali in Delhi found that they may release a higher proportion of ultrafine particles than conventional fireworks, complicating claims about how much cleaner they actually are.

A 2022 study by researchers at Delhi Technological University (DTU) found that the ratio of ultrafine particles to total particles was 0.72 for green crackers, compared with less than 0.6 for traditional fireworks. While the findings do not establish that all green crackers are more polluting, they raise questions about how their environmental impact is measured and what their certification standards actually guarantee.

Developed by the Council of Scientific and Industrial Research (CSIR), with the National Environmental Engineering Research Institute (NEERI) playing a key role, green crackers use modified chemical formulations and manufacturing techniques intended to reduce emissions. But how much pollution do they actually prevent, and what does the research say about the particles they release?

What exactly are green crackers?

Green crackers are fireworks developed to reduce the pollutants released during combustion. They use modified chemical formulations, reduced quantities of certain raw materials and additives intended to improve combustion efficiency or suppress particulate emissions.

Unlike conventional fireworks, which can release substantial amounts of particulate matter, sulphur dioxide (SO₂), nitrogen oxides (NOx) and metals, green crackers are designed to produce lower emissions of specified pollutants while retaining their intended sound and visual effects.

According to CSIR-NEERI, green crackers are developed using modified chemical formulations and are assessed against conventional fireworks belonging to the corresponding category. The institute's current emission criteria require a reduction of at least 30 per cent in particulate matter emissions. Alternatively, a product can qualify through a reduction of at least 20 per cent in particulate matter alongside a minimum 10 per cent reduction in gaseous emissions.

CSIR-NEERI tests firecrackers in a dedicated emissions-testing facility, measuring particulate and gaseous emissions against conventional formulations in the same product category. Products are also assessed for noise emissions and prohibited chemicals as part of the testing process.

These criteria do not mean that green crackers are pollution-free. They still release smoke and particulate matter, and the extent of emission reduction varies by product.

Who developed green crackers and why?

The Supreme Court's October 23, 2018 order in Arjun Gopal v Union of India introduced restrictions on the manufacture, sale and use of conventional firecrackers and allowed the use of less-polluting alternatives subject to specified conditions. The Court subsequently clarified its directions on October 31, including the prohibition on barium salts in firecracker manufacture.

Following the intervention, the Ministry of Science and Technology announced on October 29, 2018, that CSIR scientists had developed three categories of reduced-emission fireworks: SWAS, STAR and SAFAL.

The initiative involved several scientific institutions, including CSIR-NEERI, the Central Electronics Engineering Research Institute (CEERI), the Indian Institute of Toxicology Research (IITR), the Indian Institute of Chemical Technology (IICT), the National Chemical Laboratory (NCL), the Central Electrochemical Research Institute (CECRI), the National Botanical Research Institute (NBRI) and the Central Mechanical Engineering Research Institute (CMERI).

CSIR-NEERI coordinated the development and testing exercise and is now the national nodal centre for testing and research on green crackers.

Green crackers were formally launched in October 2019, alongside a green logo and QR-code system to help consumers identify approved products.

How are green crackers different from conventional fireworks?

The main difference lies in their chemical composition. Conventional fireworks use different oxidisers, fuels and compounds to produce explosions, colours and sound. Depending on the type of firecracker, their combustion can release particulate matter, sulphur dioxide, nitrogen oxides and metals such as barium.

Green crackers use modified formulations to reduce the use of certain chemicals and improve combustion efficiency. CSIR-NEERI has developed three principal categories:

- SWAS (Safe Water Releaser): CSIR-NEERI's current technical description says SWAS uses a polymer hydrogel to capture particulate matter during bursting. The Ministry's 2018 announcement separately described the release of water vapour and/or air as a dust suppressant and diluent for gaseous emissions.

- STAR (Safe Thermite Cracker): This formulation uses iron oxide to improve combustion efficiency. CSIR-NEERI's technical documentation specifies approximately 40 per cent iron oxide in the formulation. The additive is intended to improve the burning process and reduce emissions.

- SAFAL (Safe Minimal Aluminium): This formulation uses zeolite-based materials to reduce the quantity of aluminium required. Aluminium is retained in minimal quantities, mainly for initiating the reaction.

The Ministry of Science and Technology's October 29, 2018 announcement said SWAS eliminated potassium nitrate and sulphur, while CSIR-NEERI's current technical description lists both among its ingredients. NEERI's technical documents also refer to a SWAS-HG variant, but do not clearly establish whether the differences reflect separate formulations or a subsequent revision.

Other changes include smaller shells, reduced raw materials and the elimination of ash-producing components in some formulations.

A study published in Environmental Pollution in January 2023, Green Firecrackers with Reduced Barium Emissions in Particulate Matter, examined four types of conventional and reduced-emission fireworks. The researchers, including Utkarsha Wankhede and Sadhana Rayalu of CSIR-NEERI, found that the tested green crackers had 30–60 per cent lower mean barium concentrations in PM2.5 and PM10 emissions than conventional fireworks.

The reduction varied according to the type of firecracker, shell size and quantity of chemicals used. The researchers attributed the findings to reduced use of barium nitrate and the formation of heavier compounds that were more likely to settle on the ground.

The Supreme Court had prohibited barium salts in firecracker manufacture in its October 2018 directions. The study's findings relate to the four product types tested and should not be interpreted as evidence that barium-containing crackers are permitted under current regulations. CSIR-NEERI's present guidelines prohibit barium salts, a restriction reiterated by the Supreme Court in its October 29, 2026 order.

Green crackers are also assessed for noise emissions. CSIR-NEERI's technical documentation specifies a sound-emission limit below 125 dBA.

Are green crackers really less polluting?

A study published in the Journal of Environmental Management in September 2022 by Shailendra Kumar Yadav, Rajeev Kumar Mishra and Bhola Ram Gurjar examined particle emissions during Diwali 2019 at Delhi Technological University's campus.

The researchers monitored particle number concentration and particle-size distribution, measuring how many particles were present in the air and how large or small they were.

They recorded an average particle number concentration of approximately 1.29 lakh particles per cubic centimetre between 6 pm and 10 pm on Diwali. The concentration peaked at approximately 1.7 lakh particles per cubic centimetre around 7.30 pm.

The study reported an ultrafine-particle-to-total-particle ratio of 0.72 for green crackers, compared with a figure of less than 0.6 cited for traditional fireworks. The researchers observed that green crackers "emit more particles with smaller diameters than traditional crackers".

Ultrafine particles are generally defined as particles with a diameter of 0.1 micrometres or less. They are a subset of PM2.5 and can penetrate deep into the lungs. Unlike conventional particulate-matter measurements, which calculate particle mass, particle number concentration measures how many particles are present in a given volume of air.

The World Health Organization's 2021 Global Air Quality Guidelines include good-practice statements on monitoring and managing ultrafine particles. The organisation recommends measuring them through particle number concentration but says there is insufficient quantitative evidence to establish specific air-quality guideline levels for them.

The findings, however, need to be understood in the context of the study's methodology. The researchers monitored ambient particle concentrations at one location on the DTU campus during a single Diwali celebration. The study was not a controlled laboratory comparison of all green crackers and conventional fireworks, and ambient measurements can also be influenced by other pollution sources. It therefore does not establish that every green cracker releases more ultrafine particles than every conventional firework, or that green crackers necessarily pose a greater overall health risk.

Under its October 29, 2026 order, the Supreme Court has permitted only approved green crackers to be burst in Delhi-NCR on November 7 and 8, between 6–7 am and 8–10 pm. Fireworks are prohibited within 300 metres of hospitals, nursing homes, primary and district health centres, old-age homes and notified silence zones. The restriction also applies to educational institutions. Sales are permitted only through licensed traders at designated locations.

Online sales are prohibited, and each approved box must carry a product- and batch-specific QR code containing details of the manufacturer, NEERI registration, PESO/DM licence, formulation and test certificate. Barium-containing and unapproved crackers remain prohibited. The complete ban on firecrackers will be restored from November 9.

Green crackers are designed to reduce specified emissions, not eliminate pollution. Their impact depends on their chemical composition, particulate emissions and the size and number of particles released.