Friday, December 4, 2015

Mondays at the dynamite factory are particularly bad

The world is full of things capable of causing us harm: living things (e.g. pathogenic bacteria), chemical things (e.g. cancerous exhaust from a diesel engine), and physical things (e.g. any of heat, cold, noise, or ionizing radiation). Even when you just focus in on places where people work, there are a huge number of ways a person can end up hurt.

If an illness is clearly linked to doing a particular job, it tends to end up named after it. I've written about some of these afflictions before: chauffeur's fracture, coal miners' nystagmus, and trombone player's lung. In other instances, an occupational illness has acquired its name from the agent responsible for it (e.g. asbestosis and radium jaw).

Today's post is about "nitrate head", a throbbing headache caused by exposure to organic nitrates in the workplace. A nitrate is a nitrogen atom with three oxygen atoms bound to it. Sometimes one of these oxygen atoms is also attached to additional atoms including those of carbon and hydrogen, making it an organic nitrate (e.g. nitroglycerin). These nitrates are predominantly used as drugs and/or explosives.

Their use in medicine is for the treatment of heart-related chest pain (angina pectoris), which results when the heart muscle doesn't receive enough blood (and thus oxygen) via the coronary circulation. Organic nitrates are converted by the body to nitric oxide, which acts on blood vessels to cause them to widen (vasodilation). This decreases the amount of work the heart has to do, lowering its demand for oxygen and relieving the chest pain. Yay! However, the widening of blood vessels in the head and neck by nitric oxide can activate nearby pain receptors, producing an aching noggin. Boo! Since angina tends to be way more painful (and stressful) than the headache, people generally don't complain too much about this side effect.

Nitroglycerin for angina, from L to R: Injectable solution, patch, and sublingual spray (Source)

Headaches have also been observed among those who work with nitrates (e.g. soldiers, munition workers, miners, and employees at plants where angina drugs, dynamite, or rocket propellant are manufactured). Nitrate-induced headaches among workers have acquired nicknames such as "nitrate head", "powder head" (gunpowder contains potassium nitrate), "NG head" (NG = nitroglycerin), and "bang head" (nitrates are used as explosives). They generally result from inhaling nitrate-containing dusts or touching dust-contaminated surfaces.

The severity of the headaches can vary, with additional symptoms such as dizziness, having your face flush red, and feeling like you're gonna barf occurring in some cases. Being dosed up with nitrates and then drinking a bunch of the alcohol makes for a fantastic level of intoxication, with people reportedly losing their minds and becoming uncharacteristically violent. Fortunately, the headaches tend to subside with continued nitrate exposure, as the body adjusts to the effects of nitric oxide by producing compensatory responses to counteract them.

Recognized since at least 1910, when it was noted in a military officer during his service in the Boer War, "nitrate head" was particularly common during the two world wars due to a somewhat related spike in the production of explosives and ammunition. In the 1950s, UK soldiers in the Middle East apparently viewed nitrate-induced headaches as being "of nuisance value only and which they treated by lying down in a darkened room and drinking cold beer...this method of treatment achieved great repute in the Canal Zone of Egypt" (McGuinness and Harris, 1961). No mention of people losing their minds though.

Many heads were ached to produce this dynamite (Source)

Nitrate-exposed workers were susceptible to a condition known as "Monday head", where they'd feel pretty good during their weekends off only to have their headaches violently recur upon returning to work. Having recognized the cause of this ailment, lifers at nitroglycerin factories apparently would rub a bit of nitrate into their hat bands (hats were still a must-have fashion accessory at the time). This would ensure their continued exposure to nitrate while away from work, thus avoiding a particularly achy start to the week.

In addition to "Monday head", people working with nitrates have historically had a strange tendency to drop dead on Monday mornings, just prior to going back to work after a weekend off. This phenomenon of "Monday morning sudden death" has been attributed to a compensatory response by the body that only appears after the effects of nitrates wear off over a weekend. Since nitrates cause blood vessels to widen, the body responds by attempting to constrict them, returning things to normal (homeostasis). When nitrate exposure is interrupted, the blood vessels constrict, and the reduced blood flow to the heart can lead to sudden death.

"Nitrate head" and "Monday morning sudden death" are seldom observed these days thanks to the introduction of improved health and safety measures (e.g. better ventilation, reduced dust generation, and protective clothing).


References

Ebright GE. 1914. The effects of nitroglycerin on those engaged in its manufacture. Journal of the American Medical Association 62(3):201-202.

McGuinness BW, Harris EL. 1961. "Monday head": An interesting occupational disorder. British Medical Journal 2(5254):745-747. [Full text]

Warren JV. 1988. Monday morning sudden death. Transactions of the American Clinical and Climatological Association 99:10-16. [Full text]

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