Pollution in Delhi soared to hazardous levels on the night of Diwali, hitting 40 times the limit recommended by the World Health Organization (WHO).

Already one of the most polluted cities in the world, the Indian capital deteriorated even further thanks in part to firecrackers being set off to celebrate the Hindu festival of lights.

Levels of PM10 particulates - polluting particles that are so small they can settle in the lungs - soared to 2,000 micrograms per cubic metre at the height of the celebration, The Times of India reported.

WHO guidelines suggest a limit of 50 per cubic metre.

Despite an anti-firework campaign by the Delhi government, all air safety standards were reportedly breached during the festival which sees millions attend firework displays, prayers and celebratory events across the country.

Sulphur dioxide, which can lead to spikes in asthma and other respiratory diseases, was also found to be very high in areas of the city.

A 2016 study by WHO found that India has 10 of the 20 most polluted cities in the world, with Delhi placing 11th.

Diwali 2016 - In Pictures Show all 16 1 /16 Diwali 2016 - In Pictures Diwali 2016 - In Pictures Indian Sikh devotees watch a fireworks display during Bandi Chhor Divas, or Diwali, at the Golden Temple in Amritsar Getty Diwali 2016 - In Pictures People decorate their houses with lanterns and lights as they celebrate the annual Hindu festival of Diwal in Mumbai, India Reuters Diwali 2016 - In Pictures Devotees light candles at a Gurdwara, or Sikh temple, during celebrations to mark Bandi Chhorh Divas, which coincides with the Hindu festival of Diwali, in Chandigarh, India Reuters Diwali 2016 - In Pictures A girl holds a fire cracker celebrating the annual festival of Diwali Getty Diwali 2016 - In Pictures A man and his daughter hold fire cracker as Indians celebrate the annual festival of Diwali Getty Diwali 2016 - In Pictures Diwali, the Festival of Lights, marks victory over evil and commemorates the time when Hindu god Lord Rama achieved victory over Ravana and returned to his kingdom Ayodhya Getty Diwali 2016 - In Pictures Children watch fireworks at the Madan Mohan Malviya stadium on the eve of the Hindu festival of Diwali in Allahabad on October 29, 2016. Diwali, the Festival of Lights, marks victory over evil and commemorates the time when Hindu god Lord Rama achieved victory over Ravana and returned to his kingdom Ayodhya. / AFP PHOTO / SANJAY KANOJIASANJAY KANOJIA/AFP/Getty Images Getty Diwali 2016 - In Pictures Indian athletes watch fireworks at the Madan Mohan Malviya stadium on the eve of the Hindu festival of Diwali in Allahabad on October 29, 2016. Diwali, the Festival of Lights, marks victory over evil and commemorates the time when Hindu god Lord Rama achieved victory over Ravana and returned to his kingdom Ayodhya. / AFP PHOTO / SANJAY KANOJIASANJAY KANOJIA/AFP/Getty Images Getty Diwali 2016 - In Pictures An Indian athlete watches fireworks at the Madan Mohan Malviya stadium on the eve of the Hindu festival of Diwali in Allahabad on October 29, 2016. Diwali, the Festival of Lights, marks victory over evil and commemorates the time when Hindu god Lord Rama achieved victory over Ravana and returned to his kingdom Ayodhya. / AFP PHOTO / SANJAY KANOJIASANJAY KANOJIA/AFP/Getty Images Getty Diwali 2016 - In Pictures epa05608683 Indian women burn firecrackers during the Diwali festival celebrations in Bhopal, India, 29 October 2016. Diwali is known as the festival of lights and symbolizes the victory of good over evil and commemorates the Hindu God, Lord Rama's return to his kingdom Ayodhya. The festival will be celebrated on 30 October. EPA/SANJEEV GUPTA EPA Diwali 2016 - In Pictures epa05608684 Indian women light votiv candles during Diwali festival celebrations in Bhopal, India, 29 October 2016. Diwali is known as the festival of lights and symbolizes the victory of good over evil and commemorates the Hindu God, Lord Rama's return to his kingdom Ayodhya. The festival will be celebrated on 30 October. EPA/SANJEEV GUPTA EPA Diwali 2016 - In Pictures An Indian child lights candle at the Madan Mohan Malviya stadium on the eve of the Hindu festival of Diwali in Allahabad on October 29, 2016. Diwali, the Festival of Lights, marks victory over evil and commemorates the time when Hindu god Lord Rama achieved victory over Ravana and returned to his kingdom Ayodhya. / AFP PHOTO / SANJAY KANOJIASANJAY KANOJIA/AFP/Getty Images Getty Diwali 2016 - In Pictures Indian athletes watch fireworks at the Madan Mohan Malviya stadium on the eve of the Hindu festival of Diwali in Allahabad on October 29, 2016. Diwali, the Festival of Lights, marks victory over evil and commemorates the time when Hindu god Lord Rama achieved victory over Ravana and returned to his kingdom Ayodhya. / AFP PHOTO / SANJAY KANOJIASANJAY KANOJIA/AFP/Getty Images Getty Diwali 2016 - In Pictures An armed Gujarat Police jawan keeps vigil as visitors throng the illuminated Akshardham Temple in Gandhinagar, some 30 kms from Ahmedabad, on the eve of Diwali the Festival of Lights, on October 29, 2016. Akshardham Gandhinagar will be illuminated with some 10,000 oil lit lamps up to November 6, 2016. The Hindu festival of light, Diwali marks the homecoming of the God Lord Ram after vanquishing the demon king Ravana and symbolises taking people from darkness to light and the victory of good over evil. / AFP PHOTO / SAM PANTHAKYSAM PANTHAKY/AFP/Getty Images Getty Diwali 2016 - In Pictures A life-sized photo of Late Pramukh Swami is kept in front of an idol of Lord Swaminarayan at the illuminated Akshardham Temple in Gandhinagar Diwali 2016 - In Pictures Indian volunteer light 'diyas' or oil lamps in the shape of a "Jai Hind" - victory to India - to support the Indian Army during celebrations of Diwali, the Festival of Lights in Amritsar ge

Around 620,000 people in India are estimated to die prematurely every year due to air pollution.

Diwali sees millions attend firework displays, prayers and celebrations across the world every autumn.