Scars in an upside down tree

Energy may be the topic du jour but it's been the 800 lb. gorilla in the room for, oh, a couple of centuries. In a sense it's responsible for one of the greatest occupational health catastrophes of the 20th century, and a new report from CDC demonstrates once again it's still with us and killing working people. I'm talking about asbestos-related disease. Asbestos and the asbestos industry is a creature par excellance of the age of energy in the 19th century. Its primary uses were for insulating steam pipes and boilers, where heat loss was measured in dollars of coal energy down the drain. I've looked at a lot of 19th century asbestos adverts and the pitch is always the same: asbestos saves the boss money. Too bad it killed his workers. In the twentieth century another energy-related use was dominated by asbestos -- friction products, meaning brakes and clutches. One irony is that when the safety movement pushed hard for standard four wheel brakes on cars in the 1920s one result was to double the market for companies like Raybestos-Manhattan, now called Raymark Industries (or as one worker told me, "You can take asbestos out of their name but you can't take it out of my lungs!").

Asbestos is a fibrous mineral that can be spun and woven into textiles. Its tiny fibers also have the tensile strength of steel and make excellent microscopic "reinforcing rods" in insulation and asbestos cement (asbestos itself is not a good insulator but traps air pockets and air is a very poor conductor of heat). The same fibers when inhaled in lungs can create havoc. Most everyone knows that asbestos can cause several kinds of cancer but fewer realize the most characteristic disease from inhaling asbestos isn't a cancer but a scarring of the lungs that takes its name from the only thing that causes it: asbestosis. This chronic lung disease has been evident from the earliest days of the asbestos industry and it was generally accepted as a serious occupational disease by doctors no later than 1930. The fact that we killed hundreds of thousands of workers from asbestos after that date should be an everlasting shame.

Technically asbestosis is an interstitial fibrosis. What does that mean? You can think of your lungs as sort of an upside down tree. The trunk is your windpipe that has two big branches to your right and left lungs. These branch in turn, again and again until we get down to the tiny twig level. The lung branches don't conduct sap like in a tree. They conduct air and this whole branching system is also called the conducting system of the lung. It conducts oxygen from the outside down to your blood and carbon dioxide from your blood back to the outside. How does it get to the blood?

At the very tips of the tiniest twigs we have the counterpart to the tree's leaves, a tiny sac of delicate tissue intwined through which are the body's tiniest blood vessels, the capillaries. The tissue here is so thin and delicate that gas molecules can pass back and forth between the blood and the hollow sac they enclose and that's how oxygen move back and forth from the "outside" to your blood. This tissue is so delicate it has to be protected and there are a number of defense mechanisms to guard the business end (the gas exchange system) from dirt, bacteria, viruses, etc. One kind of defense involves a kind of wandering police force, immune system cells called pulmonary alveolar macrophages. Macrophage means large eater and that's what these cells are. When they see a bad guy they engulf it and once engulfed they have little bags of enzymes in side that digest it. Jaws.

But not everything is easily digestible. When a macrophage encounters an asbestos fiber it tries to eat it but the fiber proves to be tougher. Hey, asbestos resists fire and acids and corrosives. Is a little blood cell going to bother it? No. In fact the blood cell gets the fatal end of the deal. The fiber kills the macrophage which dumps all its digestive juices into the surrounding tissue, causing a tissue reaction. This reaction eventually scars. A scar is fibrous connective tissue. Now imagine where this is taking place, at the ends of the lung tree. Imagine now the space between the leaves and the twigs and the branches. That's called the interstitial space and that's where the scar tissue is being laid down: interstitial fibrosis. It's like encasing the lung in a thin fibrous net. The scarring does two bad things. It makes it more difficult for gas molecules to move back and forth from lung to blood (this is called a conductive defect). It also restricts the lungs motion. This is a restrictive defect. The restriction means you can't take deep breaths, only shallower and shallower ones, and the conductive defect means even the shallow breaths aren't as effective in exchanging gas.

The scarring process takes a long time, usually somewhere from 10 to 40 years of reasonably heavy exposure to asbestos. And your lungs are a wonderful device and they have a lot of reserve capacity. You have to destroy 80 - 90% of their function before the signs and symptoms of the scarring start to appear, although the disease is visible on x-ray earlier. In the terminal stages of asbestosis the worker becomes a pulmonary cripple, unable to even get out of bed because the exertion is too great. Then the disease ends fatally.

Now many people have some asbestosis but not enough to kill them. Some have significant deficits but it isn't fatal. But plenty of young workers are still dying from asbestosis -- which unlike cancer takes quite a heavy exposure of asbestos to give someone serious disease. An estimate of how many this is has just come out from CDC. This report also calculates the number of Years of Productive Life Lost (YPLL), a measure of premature death (before age 65). It's an economic measure, not a measure of pain and suffering. If you ever saw anyone die of asbestosis you'd know there is no price you can put on that:

Persons dying before age 65 years are considered as having years of potential work tenure lost, on the assumption that these are a worker's most productive years. During 1968--2005, asbestosis was identified as the underlying cause of death for 1,169 decedents aged 25--64 years, accounting for 7,267 YPLL. Overall, a mean of 6.2 YPLL per decedent was attributed to asbestosis during 1968--2005, indicating that, on average, decedents aged 25--64 years with asbestosis listed as the underlying cause of death died at age 58 years. Despite the decline in asbestos use and reduced exposures, the findings described in this report indicate that asbestosis-attributable YPLL continue to occur. Because asbestosis mortality typically manifests several decades after initial exposure to asbestos, much of the continuing YPLL likely is attributed to exposures experienced decades ago. During 1970--2004, the annual number of asbestosis-related deaths (based on the analysis of asbestosis deaths coded on the entity axis in multiple cause-of-death files) in the United States increased nearly 17-fold, from 89 (age-adjusted death rate: 0.6 per million persons aged >15 years) in 1970 to 1,493 (6.9) in 2000, and then declined slightly to 1,470 (6.3) in 2004, for an overall total of 25,413 asbestosis deaths over the entire period. This slight decline in the age-adjusted death rate was attributed to several factors, including reduced use of asbestos and improved control of asbestos exposure. Beginning several decades ago, increased awareness of the health consequences of asbestos exposure stimulated voluntary and regulatory actions by the Environmental Protection Agency and the Occupational Safety and Health Administration.

Available data (for 153 decedents) indicated that the greatest industry-specific YPLL values were associated with work in construction and ship and boat building and repairing, which is consistent with documented past industry-specific asbestos exposures (1). Likewise, two of the three occupations with the greatest YPLL values, insulation workers and plumbers, pipefitters, and steamfitters, are well known to have been associated with asbestos exposures.(Morbidity and Mortality Weekly Reports, CDC [cites omitted]).

Asbestos fibers in a lung are a delayed action time bomb. We've made progress in getting asbestos out of our workplaces and environment, but there is plenty still in place and still asbestos-containing products (like brakes and clutches) imported into the US and sold here. Construction workers are exposed during demolition and rip out of asbestos-containing building materials and pipe fitters and insulators still work around asbestos insulated facilities installed decades ago. Whenever I hear people complain about OSHA and workplace regulation I think of the faces of the many workers I've seen who died and agonizing death from the "magic mineral."

The only magic it performed was to turn broken bodies and lives into dollars for asbestos companies, who knew all along the damage they were doing. And the damage still goes on.