The Squatter's Barometer -- an environmental health case study

This is a true environmental public health case study with names changed to ensure dissociation with any real persons living or dead.

It was a crisp, sunny winter day when my colleague received a call about a residential mercury spill. What made this spill a singular one was twofold: the former residential property was technically vacant and the single occupant was a squatter who had temporary permission to stay there.

The two-acre property in question had a small dilapidated abandoned residence surrounded by a large wooded lot nestled among million dollar homes. The property was listed for sale for more than half a million dollars; however, a homeless person, Mr. Oxford, had taken up residence in the remaining livable three rooms of the home. When discovered by the property owner, he was given permission to stay through the winter in exchange for keeping an eye on the place.

Mr. Oxford said that he had recently been shopping on-line using a not-for-profit website and came across an attractive antique mercury barometer for sale. He said he purchased it at a very low price and with minimal shipping costs it had been delivered from the Pacific Northwest to his temporary winter residence 5 days earlier. Upon opening the box, he found the barometer was broken. As he unpacked the box, he spilled liquid mercury in the home.

Many states prohibit the sale and distribution of mercury-added products, including barometers, so the not-for-profit likely committed at least a petty offense by selling and shipping the old barometer. At the time of the incident, we found several mercury-containing barometers available for purchase on eBay.

Antique barometers may contain up to 65 milliliters (mL) of liquid mercury. With a density of 13.5 grams per mL, that’s roughly 900 grams (about 2 pounds). Mr. Oxford was able to recover about 7 mL of mercury, which meant as much as 58 mL might still be at large in the home. Compared to an oral mercury thermometer (0.5 grams) or a mercury-containing blood pressure device (150 grams), this was a large spill.

We dispatched an environmental health specialist to the scene armed with a mercury vapor analyzer. The following levels were detected in the home in units of nanograms per cubic meter (ng/m3):

Unheated front porch: 16,900 ng/m3

Box with broken barometer: 37,700 ng/m3

Entry hallway: 48,000 ng/m3

Living room/bedroom: 26,100 ng/m3

Kitchen: 7,400 ng/m3

Bathroom: 11,600 ng/m3

For comparison purposes, our acceptable level for occupancy of any residential structure after a mercury spill is 1,000 ng/m3.

Mr. Oxford had opened the parcel in the living room/bedroom, and then carried the leaking box out to the front porch through the entry hallway. The presence of mercury and vapor in the kitchen and bathroom were likely due to tracking and air circulation.

We advised Mr. Oxford and the property owner that the home should be vacated and that the tenant’s personal effects were likely contaminated. With nowhere else to go, alternative living arrangements for the tenant were arranged through the property owner and local health department. 

We contacted USEPA emergency response staff with our findings and they sent out remediation contractors to confirm our sampling results and to effect cleanup. Spilled mercury is difficult to clean because the droplets spread readily and sink into cracks and crevices in flooring material. Typical cleanup costs exceed $10,000.

By 6 p.m. the following day, USEPA reported a successful clean up evidenced by mercury vapor levels less than 1,000 ng/m3 throughout the home.

Because Mr. Oxford had been exposed to elevated levels of mercury vapor for about 5 days, we referred him for medical follow up with occupational medicine partners in the area. He reported no symptoms, which reasonably could have included cough, sore throat, nausea, headache, or visual disturbances.

This case illustrates that despite regulation, mercury-containing items still are available for purchase and that resulting mercury spills can be dangerous to human health and costly to clean up, even in exceptional and challenging situations such as this one.