DANGEROUS viruses are being spread around the world through the sewage held in aircraft, according to a new survey. Out of 40 samples of sewage pumped from international flights landing at two major American airports, 19 contained infectious viruses that had survived exposure to disinfectant chemicals in the aircraft鈥檚 sewage tanks.
鈥淚t was a bit of a jolt for us,鈥� says Mark Sobsey, an environmental scientist at the University of North Carolina in Chapel Hill, who led the study, speaking at the American Society for Microbiology meeting.
Sobsey was asked by his sponsors, the WHO and the US Centers for Disease Control and Prevention in Atlanta, Georgia, to search the sewage samples for enteroviruses, in particular the polio virus. The researchers were pleased to find that the samples did not contain live polio viruses. However, other enteroviruses, which cause symptoms from stomach upsets to fever and nausea, were present.
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As well as polio, the enterovirus group includes potentially lethal echoviruses and Coxsackie viruses, which can cause meningitis and myocarditis, an infection and inflammation of muscles in the heart.
Sobsey fears that other dangerous viruses that can be transmitted by sewage, such as hepatitis A and E, may also survive current sterilising treatments. 鈥淭he range of illnesses that can be transmitted by the world鈥檚 airlines is quite worrisome,鈥� says Sobsey. 鈥淲e think there are probably bacteria and parasites as well.鈥�
In the US, waste pumped from passenger aircraft is usually treated in municipal sewage works, says Sobsey. But conventional sewage treatment often eradicates only 90 per cent of viruses. 鈥淭hat means 1 to 10 per cent of the viruses survive and are discharged into the environment,鈥� he says.
So 鈥渁lien鈥� viruses could be released into the environment in countries in which they do not usually occur. 鈥淲e think there鈥檚 a risk and we should pay more attention to the hazards posed by international travel,鈥� says Sobsey. In some countries, he adds, aircraft are frequently forced to discharge saturated sewage tanks untreated. 鈥淚f the [sewage treatment] system鈥檚 full, they don鈥檛 have any choice but to dump.鈥�
Airline sewage tanks currently contain disinfectants based on ammonium salts. Sobsey wants airlines to consider adding glutaraldehyde, a water-soluble oil that is highly active against viruses. Some airlines have already adopted glutaraldehyde, says Sobsey. It can be added to aircraft sewage tanks at virtually no extra cost, he adds.
A spokesman for the Montreal-based International Air Transport Association, which represents the world鈥檚 major airlines, says that the association would need to examine Sobsey鈥檚 findings in more detail before commenting.