What Makes Manholes So Lethal?

Without safety equipment, workers inside manholes are exposed to three dangerous environments conspiring together: chemical, biological and legal.

Manholes are brutal environments that can quickly translate a callous attitude, lack of emergency response protocols and the absence of basic safety equipment to death. Contractors have been known to cut costs and to try to get the ‘job’ of cleaning them done quickly, and not equip workers with ventilators, gas concentration detectors, gloves, face masks and hard hats (as well as not keep a person on standby on the outside to help in case of an emergency). As a result, the workers are left exposed to three dangerous environments conspiring together: chemical, biological and legal.

If workers are made to enter drains, they will have to be trained to understand the threats that can arise and equipped such that the best way they can respond can actually be executed as fast as possible. Such environments often have very little space to move around and accidents can quickly lead to death, so having a protocol that optimises for time is important.

However, designing and implementing such a protocol for various accident scenarios would be to assist skilled workers such as engineers, hydrologists, etc. Expecting an unskilled worker and unequipped worker to enter a confined and septic environment to clean it is to wilfully endanger their lives.

For example, one of the biggest threats in a drain is noxious gases and vapours. Once they begin to leak from, say, a damaged pipe, their concentration can build quickly, making the air unbreathable.

Need for technology

These gaseous products are commonly collected under the term ‘sewer gas’. According to the Wisconsin Department of Health Services, “Sewer gas is a complex mixture of toxic and nontoxic gases that can be present at varying levels depending upon the source.”

Drains contain abundant organic matter. When they decompose in the absence of oxygen, they produce hydrogen sulphide, especially if the environment is warm and the sludge has been stagnating. Hydrogen sulphide is soluble in water and becomes trapped in sewage matter. When the latter is disturbed, the gas leaks out and causes nausea, delirium and convulsions, which can all imperil self-rescue. It is also a skin and eye irritant.

When absorbed through the lungs, it causes pulmonary oedema. If it is present in the sludge at 1 mg per litre or more, it can accumulate in the air at hundreds of parts per million and knock a person out. According to one estimate, workers shouldn’t be exposed to 2 parts per million of the gas for more than 30 minutes. At over 1,000 parts per million, hydrogen sulphide can kill in a single breath.

The gas has a foul smell resembling that of rotten eggs, and the human nose can identify it even when its concentration is as low as 0.5 parts per billion. However, expecting workers to exit the drain when it becomes stronger is a bad strategy. This is because of a condition called olfactory fatigue. Because of the way the olfactory system is organised in the human brain, receptor cells that trigger electric signals in response to the smell stop firing after a while. In colloquial terms, we stop smelling a smell once we’ve smelled it enough.

The US National Institute of Health defines this fatigue as “the temporary normal inability to distinguish a particular odour after a prolonged exposure to that airborne compound”. This is why it is more dangerous for humans to work inside drains – one of their sensory faculties stops being able to sense threats. If a worker must enter the drain, then they must be equipped with detectors to alert them to the presence of a potentially deadly compound in the air.

Another thing to consider is the relative density of gases.

When fuel is burnt inside, in that already oxygen-poor environment, the combustion process uses up the gas and releases carbon monoxide. (If fuel is combusted in the presence of hydrogen sulphide and methane, there can also be an explosion.) And when methanogenic bacteria are present in the biofilm lining the plumbing’s inside, methane is produced.

When all three gases – hydrogen sulphide, methane and carbon monoxide – are present, they don’t assault the worker at the same level. Instead, they become stratified by height. Methane rises to the top because it is the least dense. Carbon monoxide becomes sandwiched in a layer between the methane on top and the hydrogen sulphide below. The latter two are both denser than air. Finally, because methane is also less dense than air, it displaces air.

All together, a worker is left stranded in an environment where there is breathable air only outside the drain system, not inside, making asphyxiation a likely outcome.

With so many known risks, and possibly more unknown ones, drainage work ought to be completely mechanised – as the Prohibition of Employment as Manual Scavengers and Their Rehabilitation Act 2013 also insists. In the off chance that a drain has to be cleaned manually, the Act also lists no less than 44 pieces of equipment they must carry on their person (Rule 44).

However, the same Act also makes room for exceptional circumstances in which machines can’t be used, and all instances of unskilled workers working inside drains are shoehorned into this small loophole. This is why we often see workers working with nothing but their clothes on.

And even if chemical or chemically motivated hazards don’t get to the workers, the bacterial ones certainly will.

Microbial threats

Before the 1870s – i.e. before the advent of medical bacteriology – toilets had to have their plumbing regularly replaced to prevent sewer gas from entering living quarters. And those most affected belonged to the upper class because only they owned houses with indoor toilets. As a result, sewer gas was an affliction of the rich.

In 2001, James Whorton, then of the department of medical history and ethics, University of Washington School of Medicine, Seattle, wrote of an interesting episode in the American presidency involving sewer gas:

When President James Garfield was shot in 1881 and taken to the White House to be treated, his steady decline over the following weeks at last came to be blamed not on the assassin’s bullet still lodged in his back, but to the executive mansion’s obsolete plumbing system. A “well-known plumber” told a New York newspaper that “the real trouble” in Garfield’s case “is sewer gas,” while the Sanitary Committee of the Master Plumbers of New York offered to outfit the White House with sewer traps at no charge. Instead, the president was moved from Washington, DC, to his summer home in New Jersey, despite physicians’ fears that he could not survive the journey; he died in New Jersey less than two weeks later.

His successor, Chester Arthur, refused to move into the White House, having been made nervous by authoritative statements that, until its plumbing was reconstructed to eliminate sewer gas, “the White House will be behind our better class of tenement-houses.” Arthur even went so far as to lobby Congress to tear down the White House and erect a sewer gas-proof replica in its stead, but though the Senate approved $300,000 for the project, the House of Representatives would not concur, and the new President had to settle for a plumbing overhaul of the old building.

Bacteriology taught us that a chemically dangerous environment is closely linked to its biological counterpart. Stagnating sewage encourages the formation of bacteria, viruses and parasites. Sewage containing antimicrobial substances can engender antibiotic resistance, especially if the faecal load is high, leading to new and potentially deadly strains that can contaminate groundwater and sources of drinking water exposed to untreated waste.

For example, studies have already recorded the presence of bacteria resistant to methicillin, beta-lactams and carbapenems in India and vancomycin elsewhere – in sewage. And the problem will only worsen with climate change thanks to the heightened incidence of rainfall and urban flooding.

The most common symptoms of infections among drainage workers include watery diarrhoea, nausea, fever, jaundice and typhoid. Uncommon, but nonetheless dangerous, effects include haemolytic uraemic syndrome, paralysis and kidney failure.

One of the biggest threats in a drain is noxious gases and vapours. Credit: Arpita Singh and Mayank Chawla

One of the biggest threats in a drain is noxious gases and vapours. Credit: Arpita Singh and Mayank Chawla

The drugs to treat many of these infections are becoming increasingly useless while the pathogens are having increasingly debilitating effects. There is already a debate raging over the Indian government’s plan to make bedaquiline available to people with drug-resistant tuberculosis. For a subset of the 1.4 lakh people thought to have this form of the disease, bedaquiline is often the last option before death (with a success rate of 63%).

Some bacteria also exacerbate mechanical failures in the plumbing and can cause widespread damage if the sewage is not treated properly. For example, bacteria called Acidithiobacillus thiooxidans oxidise hydrogen sulphide to sulphuric acid, which then corrodes metal pipes. A 2012 study implicated bacteria of the genera Acidiphilium, Mycobacterium, Xanthomonadales, Burkholderiales and Sphingobacteriales in similar deleterious processes.

Hemmed in

It is horrible that many workers in India are forced to work in conditions that combine all these ghastly threats, often being unable to access affordable and high-quality healthcare when they most need it. When workers do die, the final nail in their coffin is often the law. For example, companies with fewer than ten employees that engage in work of this nature and of value less than Rs 10 lakh per project are outside the purview of the Factories Act 1948 and Building And Other Construction Workers Act 1996.

As a result, when two young men died in June 2016 in a tank they were working in on the Anna University, Chennai, campus, after inhaling toluene, their employer faced no sanctions about maintaining poor working conditions. Instead, the deputy commissioner of labour only consulted with the company and Anna University to provide compensation for the workers’ families, which was also capped at Rs 11 lakh by the Employees Compensation Act 1923.

This is not a unique case. According to the International Labour Organisation, India hasn’t yet ratified over 50 conventions on the rights of labourers. Seven of them pertain to occupational health and safety (the oldest from 1981).

The changing nature of labour, particularly in the ‘gig economy’, has excluded millions of Indians from legal safeguards, while instruments like Aadhaar are making it harder for them to access medical care and food. Rule 6 of the Prohibition of Employment as Manual Scavengers Act 2013 even expressly requires workers to be able to access “regular vaccination against respiratory and skin diseases and other occupational diseases”.

The Ministry of Labour recognised these issues in a policy document published in 2009, but nine years later, nothing has changed.

#Grit is a new initiative of The Wire dedicated to the coverage of manual scavenging and sanitation and their linkages with caste, gender, policy and apathy. The Manual Scavenging Project is the first in a series of deep dive editorial projects.

Join The Discussion