by Josh Thompson
Industrial Hygiene Technician
Asbestos is a family of naturally occurring, fibrous silicate minerals which have been mined for thousands of years due to their usefulness as an additive in various products. In the recent past, asbestos has been used in myriad building materials, including gypsum wallboard, joint compound, various floor and ceiling tiles, transite siding and many others. Asbestos was added to these building materials as it increases structural integrity, increases fire resistance and acts as a thermal and acoustic insulator. While these added benefits extended the life and usefulness of asbestos containing building materials, the adverse health effects to individuals exposed to asbestos fibers far outweigh any perceived benefits. The earliest documented concerns about asbestos dangers arose from observations of health problems in asbestos workers, notably in the late 19th and early 20th centuries. Specifically, British factory inspectors and medical professionals observed increased rates of lung disease and premature death among asbestos textile workers. These early findings, along with autopsy reports revealing asbestos fibers in the lungs, led to the recognition of asbestosis as a work-related disease.
While the negative health effects of asbestos on the human respiratory system have only been studied for a little over a century, asbestos has been utilized by humans since at least the Paleolithic era. One fascinating archaeological site in Finland has provided some of the earliest examples of manmade, asbestos-containing materials. In the 1960s, excavations on Kierikki-saari Island in northern Ostrobothnia, Finland, uncovered pottery sherds which contain asbestos as temper. Pottery temper is a material added to clay to improve its workability and prevent issues like cracking and warping during the drying and firing processes. It essentially helps to make the clay more predictable and durable, and helps with shrinkage and cracking in the clay, as well as thermal shock during the firing process. Asbestos temper was used in this area due to its local availability and because of the added structural integrity provided by asbestos fibers, for similar reasons as why asbestos has been used in more modern building materials. The pottery found at the Kierikki-saari site has been typologically described as “Kierikki-ware.”
Kierikki-ware pottery has only recently been dated using radiometric methods. In 2018, Archaeologists Teemu Mokkonen and Kerkkko Nordqvist published the first AMS (Accelerator Mass Spectrometry) dates for organic elements found within the pottery. AMS dating is a technique used to determine the age of organic materials by measuring the amount of carbon-14 remaining in a sample. Carbon-14 is a radioactive isotope of carbon that is constantly produced in the upper atmosphere and incorporated into living organisms. Once an organism dies, it stops taking in carbon-14, and the existing carbon-14 begins to decay at a known rate (half-life of 5,730 years). By measuring the remaining carbon-14 and comparing it to the known decay rate, scientists can estimate the time since the organism died. 15 samples of charred organic residues and birch bark pitch found included in the pot sherds were dated using AMS dating, which was then calibrated by dendrochronology, or tree ring dating. By analyzing the annual growth rings of trees, dendrochronologists can create a precise timeline of past atmospheric carbon-14 levels. These two methodologies are used in concert to provide a narrower margin of error, in this case ≥± 70 years. This AMS dating provides a range of 3650-2700 calBC, or roughly 5600-4700 years ago. While it is difficult to create a full typology for Kierikki-ware due to the fragmented nature of the pot sherds recovered, this archaeological site has also yielded stone tools, as well as post holes thought to be the remnants of wooden structures on the island. Kierikki-saari is also unique as pot sherds found at the site almost exclusively contain asbestos as temper. Due to the amount and variation of material culture found, the Kierikki-saari site has become one of the best studied neolithic site in Finland. This site provides a unique look into prehistory and one of the earliest known uses of asbestos in material.
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