What has rope got to do with health?
At this writing, we are three months into winter. New England lobstermen may have spent a good deal of that time indoors working on gear. Sanding and painting buoys (painting outside, and with low VOC paint) and working indoors with rope (looking for weak spots; splicing pieces; inserting weak links) are typical activities during the winter months.
Some lobstermen may not have felt well. What was going around? The list included COVID-19, flu, colds, and Respiratory Syncytial Virus (RSV). These ailments seem to have some symptoms in common such as congestion, cough, runny nose, sore throat, fever, headache, and tiredness.
There are, however, some differences in terms of how long mild forms of these ailments last: flu may last 5-7 days; colds 7-10 days; COVID-19 and RSV – two weeks.
The peaks in hospitalizations for all these illnesses for ages 18-49 and 50-64 were early December for flu and over the December/January holiday for COVID-19. Hopefully, we are beyond the highly-infectious time for flu and COVID-19.
But perhaps you were a lobsterman who was working indoors with rope – splicing, adding weak links, or handling a lot of used rope. You could easily have been inhaling dust from that old rope.
And suppose, during the period from January to March, you had a cough or congestion that persisted for more than the one-to-two weeks common to the illnesses mentioned above. What then?
With those symptoms, it’s likely you thought you had a cold, the flu, or even COVID-19. But perhaps your symptoms persisted – you felt that way all winter, it seemed.
It is possible that endotoxin in the rope dust was the cause of your persistent respiratory symptoms.
What is endotoxin?
Endotoxin is a material left over when gram-negative bacteria die. Endotoxin is present in very low levels in the environment. It is present in higher levels in rural areas and in even higher levels in agricultural settings or where textiles are processed.
For fishermen, endotoxin can be present in substantial concentrations on trap rope. The basic sequence: algae and seaweed collect on the rope; bacteria are present on the algae and seaweed; when the rope is out of the water, the algae die, then the bacteria die; the dust that is left contains endotoxin from the gram-negative bacteria.
Gram-positive bacteria, even if present, do not leave endotoxin behind when they die.
Figuring it out
Nearly 20 years ago, I took Earl Dotter, a nationally-known photographer of hazardous work, to Vinalhaven, Maine. I set up an immersion suit training in the quarry with several fishermen which Earl photographed; he took wonderful portraits of individual fishermen; and, at the end of the day, he photographed the catch unloading and weighing process when the fishermen returned to the harbor.
During that day, we visited the local clinic and asked Dr. Rick Donahue (the island’s doctor at that time) what health issues he saw among Vinalhaven fishermen. Dr. Donahue replied without hesitation that he was mystified why so many fishermen came to him with respiratory symptoms that wouldn’t go away during the period January through March.
A few weeks later, I returned with three exposure scientists from the Harvard School of Public Health. They measured particulate matter levels and noted the presence of volatile organic compounds (VOCs) in a lobsterman’s workshop while the lobsterman did his usual work: sanding and heat-branding buoys and manually inspecting trap rope.
On a whim, one researcher decided to check for endotoxin. He took some rope back to the lab and performed what was then the state-of-the art assay on the sample.
And guess what? The endotoxin level was much higher than the background endotoxin level measured in Boston. (See FISH SAFE: Rope, buoy cleaning; endotoxin dust. CFN 31[10]:12B)
Endotoxin exposure occurs when dust from trap rope is inhaled. Typical endotoxin exposure symptoms include cough or persistent cough, with or without phlegm; tightness of chest; shortness of breath; increased susceptibility to lung infection; and loss of pulmonary function with continued exposure.
The problem is, because the symptoms of endotoxin exposure are similar to those of flu, colds, and COVID-19, it is difficult for healthcare providers to differentiate between this exposure and the illnesses. However, a good history-taking by that same healthcare provider would include questions about work and work environment – and the answers to those questions might point to the symptoms having resulted from a workplace exposure. A physician trained in occupational medicine would likely recognize these symptoms and their cause quite readily or at least know how to research the potential workplace exposures.
The emerging field of biofilms
Taking a little detour into biofilms, we know that biofilms are a collection of microorganisms that accumulate on living (algae) and inanimate material (plastics).
In a 2021 review article entitled, “Microbial Life on the Surface of Microplastics in Natural Waters,” Stabnikova, et al. summarize their findings by stating that all the dominant microorganisms in biofilms that cover microplastic particles are gram-negative bacteria. These biofilms often consist of different kinds of bacteria at different times in the life of the biofilm. (Biofilms have their own eco-system.) Surprisingly, different kinds of bacteria prefer different types of plastic. For example, the Alphaproteobacteria prefer the polyvinylchloride (PVC) plastics such as lobster buoys and the coastal marine environment.
The take-home messages are that there are biofilms of gram-negative bacteria on algae, on the microplastics that are lodged among the algae, on poly rope, and probably on the lobster buoys. Although a few of these bacteria may pose health problems, they are not a problem in terms of endotoxin until the bacteria die and we inhale the endotoxin that is left behind as dust.
To reduce exposure to endotoxin on trap rope, the rope should be dunked in a hot water bath (such as the hot tank that some fishermen have on board) or put through a dilute chlorine bath.
Perhaps also acceptable would be a good rinse after being sun-dried, then dried again before working on it.
Regarding the PVC buoys, they probably do not present much of a problem, but they do “live” at the air/water interface that these biofilms enjoy.
The good news is that endotoxin-related symptoms will likely disappear once fishermen are no longer working intensively with rope and are back on the water.
Welcome spring!
Ann Backus, MS, is the director of outreach for the Harvard T.H. Chan School of Public Health’s Department of Environmental Health in Boston, MA. She may be reached by phone at (617) 432-3327 or by e-mail at <abackus@hsph.harvard.edu>.
