Choking on the facts

When the World Trade Centre came crashing down, the casualties and the impact were obvious. But you may have heard of a new threat to New York City which some worry is more insidious – the ‘World Trade Centre cough’.

According to one US journalist: ‘Just as people once traded tragic stories about lives lost in the terror attacks…New Yorkers now circulate stories about people whose health has been injured in the line of duty.’ (1)

Estimates of how many people suffer from the WTC cough vary dramatically, because they are based on anecdotal evidence. Some claim there are a few hundred cases; the Uniformed Firefighters’ Association estimates that about 3000 of its members suffer from it; while the National Resources Defense Council claims there are 10,000 cases.

The implications are pretty big. A new bill in the New York State legislature proposes to extend workers’ compensation benefits to rescue and recovery personnel at the Trade Centre for ‘exposure-related illnesses’ (2) – which will presumably include the WTC cough. Meanwhile, 1300 people gave notice in early February 2002 that they may sue New York City for as much as $7.8billion ‘over the aftermath of the WTC attack’. And the Federal Emergency Management Agency is both coordinating the professional cleanup of Manhattan buildings and footing the bill (at a projected cost of $12million).

Politicians, activists and lawyers have all identified the WTC cough. It envelopes a vague collection of symptoms and ailments, including colds, asthma, nosebleeds, headache, sinus infection, pneumonia, bronchitis, nasal congestion, diminished lung capacity, hoarseness of voice, chest tightness, flu, and, of course, coughing. But are all these ailments connected? And if so, what might have caused them?

Many environmental health researchers claim that the release of toxic pollutants on 11 September caused the WTC cough. The mix of dust, melting steel, jet fuel, asbestos and dozens of other chemicals spread around Manhattan, often in huge plumes which took days to dissipate. The Environmental Protection Agency (EPA) claimed to have tested the air, and told residents it was safe to breathe.

But ‘independent tests’, and there are lots of them, have found elevated levels of all kinds of substances in and around Lower Manhattan, ranging from fibreglass to PCBs. Dozens of private firms have run tests for pollutants, but the results are usually controversial. There are many methods of testing for each pollutant and getting people to agree on one can be difficult, if not impossible. Many of the testing methods used are either not acknowledged or not understood by federal scientists.

Professor Thomas Cahill of the University of California at Davis was one of the first researchers to go public with his test results – claiming to have analysed the air pollution at Ground Zero, finding lots of ultra-fine particulate matter in the process. Cahill told New York congressman Jerold Nadler’s hearing in February that the EPA had the technology and resources to do the same tests, but chose not to.

Indeed, tests with wickedly high levels of sensitivity can detect such ‘ultra-fine’ particles (.001 inches in diameter – but the higher the sensitivity, the higher the chances for false positives (3). That may be the reason the EPA chose not to run those kind of tests.

Also, scientists are not even certain that these substances, even in large doses, can have a negative impact on people’s health. The presumed minimal exposure over a short period of time makes it unlikely there will be any noticeable health effects that can be tied to the substances themselves.

USA Today quotes Manhattan resident Dennis Gault, who worries that, ‘for a three-year-old, there are no safe levels of toxins’ (4). Most scientists, who deliberately set safety limits for toxic exposure levels lower than doses at which any health effects could be detected, do not share Gault’s opinion. While the many different tests that found ‘elevated’ levels of some substances may be cause for concern, they should not necessarily scare the bejeebers out of Manhattanites or their children.

Still, some scientists believe that the scientific understanding of safe levels for individual toxins overlooks the possibility that, taken together, they may combine synergistically, creating unsafe effects far in excess of their simple addition. This argument was invoked in some media coverage, raising fears that although the toxic exposure at Ground Zero may have been minute, the combination of substances might have caused adverse health effects.

But the best known example of synergistic effects, involving endocrine disrupting chemicals, turned out to be based on a study so pathetic that it could not be replicated. The study’s authors eventually retracted it (5).

There is no shortage of people researching the possible health impacts at Ground Zero. The Mount Sinai School of Medicine is monitoring pregnant women for possible exposure outcomes. The fire department is monitoring all of its potentially exposed emergency personnel. Queens College doctors are trying to study all of the day labourers that helped with the clean-up operation. Dr Steven Markowitz of Queens College ran a mobile van offering healthcare to day labourers, and was ‘surprised by how many people flocked to us for free medical advice, many of whom were sick months after having stopped clean-up work’ (6).

Unfortunately, the doctor shouldn’t have been so surprised. Workers on the low end of the socioeconomic pole are unlikely to have medical insurance or to receive regular health examinations, and are prone to poor diet and exercise. Day labourers are strong candidates for health problems anywhere, not just in Manhattan, inevitably skewing the results of any study.

The New York Academy of Medicine is trying to build a registry of everybody who worked for even a moment at Ground Zero – which would make the environmental health studies significantly more accurate. Even so, all the studies will be confounded by the city’s demographics, which mix residents, tourists and commuting office workers. Many of them no longer live or work there. And because we lack good data about the number of people exposed, epidemiological estimates based on these studies will be weak at best. There will be no way to accurately derive a sample of the ’11 September population’.

Experienced emergency workers have pointed out that the destruction of the Twin Towers, despite its frightening scale, did not differ that much from other disaster scenes, like Oklahoma City. Despite the myriad of tests and studies under way, there are other possible explanations for the WTC cough than toxic exposure.

Kerry Kelly, chief medical officer of the New York City Fire Department, told the Washington Post that the number of firefighters who have taken medical leave because of stress and respiratory problems had doubled since 11 September (7). But this isn’t so surprising. Menlo Park deputy fire chief Ed Greene, whose force sent many volunteers to Ground Zero, told the San Francisco Chronicle that ‘it’s not unusual for firefighters to come back from an operation with colds or other ailments, especially after a lengthy, exhausting deployment that batters the immune system’ (8).

Presuming that we can even lump together all those disparate symptoms and illnesses under one simple rubric, what could have brought on the WTC cough? Stress, fatigue, seasonal allergies and seasonal illnesses are all likely candidates. Exposure to any kind of dust, toxic or not, is bound to aggravate any of the above ailments – but not necessarily cause them.

Media coverage of the WTC cough has mostly focused on political stories: an alleged EPA cover-up; officials so eager to reopen Manhattan for business that they sounded the ‘all-clear’ without sufficient evidence; and legislative and courtroom jostling for money. Scientific and medical issues have only been raised to colour the political narratives. Approaching from the other direction – science, first – makes the stories much more accurate – even if a bit less exciting.

This an edited version of an article first published on TechCentral Station.

Howard Fienberg is senior research analyst with the non-profit non-partisan think-tank the Statistical Assessment Service (STATS), in Washington, DC.

Read on:

Anthraxiety, by Dr Michael Fitzpatrick

(1) Francesca Lyman, MSNBC, 11 March 2002

(2) AP, 7 April 2002

(3) See Mexican Jumping Genes, TechCentralStation, 18 March 2002 for an illustration of the perils in false positives

(4) USA Today, 7 February 2002

(5) See STATS’ original coverage and the follow-up

(6) MSNBC, 11 March 2002

(7) Washington Post, 12 February 2002

(8) San Francisco Chronicle, 25 December 2001