Could the Health Decline of Prehistoric California Indians Be Related to Exposure to Polycyclic Aromatic Hydrocarbons (PAHs) from Natural Bitumen?

Article excerpt

BACKGROUND: The negative health effects of polycyclic aromatic hydrocarbons (PAHs) are well established for modern human populations but have so far not been studied in prehistoric contexts. PAHs are the main component of fossil bitumen, a naturally occurring material used by past societies such as die Chumash Indians in California as an adhesive, as a waterproofing agent, and for medicinal purposes. The rich archaeological and ethnohistoric record of the coastal Chumash suggests that they were exposed to multiple uptake pathways of bituminous PAHs, including direct contact, fume inhalation, and oral uptake from contaminated water and seafood.

OBJECTIVES: We investigated the possibility that PAHs from natural bitumen compromised the health of the prehistoric Chumash Indians in California.

CONCLUSIONS: Exposure of the ancient Chumash Indians to toxic PAHs appears to have gradually increased across a period of 7,500 years because of an increased use of bitumen in the Chumash technology, together with a dietary shift toward PAH-contaminated marine food. Skeletal analysis indicates a concurrent population health decline that may be related to PAH uptake. However, establishing such a connection is virtually impossible without knowing the actual exposure levels experienced by these populations. Future methodological research may provide techniques for determining PAH levels in ancient skeletal material, which would open new avenues for research on the health of prehistoric populations and on the long-term effects of human PAH exposure.

KEY WORDS: bioaccumulation, biomarkers exposure, bone and cartilage, cultural practices, diet and nutrition, environmental epidemiology, indigenous peoples, molecular epidemiology, polycyclic aromatic hydrocarbons, population health. Environ Health Perspect 119:1203--1207 (2011). http:// [Online 19 May 2011]

In the modern world, our environment abounds in polycyclic aromatic hydrocarbons (PAHs) derived mainly from fossil fuels formed by the anaerobic decomposition of dead organisms over millions of years. The lipophilic PAHs, which chemically consist of two or more condensed aromatic benzene rings and occur in a large number of isomers, are readily taken up by the human body and distributed to different organs and tissues, including the fetus. Significant health problems such as cancer, altered hormone levels, damage to internal organs including the nervous system, and deficiencies in important nutrients such as vitamin A have been associated with exposure to liquid and atmospheric PAHs (Bostrom et al. 2002; Li et al. 2003; Mastrangelo et al. 1996; Westerholm et al. 1988, 2001). Such exposure can originate from gasoline and diesel combustion, fossil fuel processing, road paving, roofing, and tobacco smoking. PAH exposure has also been associated with reproductive and developmental impairments, including reduced birth length and head circumference in children of women exposed to PAHs during pregnancy (Choi et al. 2006; Petera et al. 1998; Polahska et al. 2010). Occasionally, extraordinary events such as major oil spills result in drastic PAH exposute, which may have severe consequences for human and animal life (Hickenetal. 2011; Wells et al. 1995).

In the ancient world, our ancestors encountered PAHs mostly in the form of fossil bitumen, or asphaltum. Fossil bitumen occurs in geological strata all over the planet. In petroleum-rich areas such as California, Mexico, and the Near East, certain geological formations allow bitumen to seep spontaneously to the surface of the eatth. Because of its adhesive and watet-repellent properties, bitumen was collected from natural seeps by early human populations and used for a variety of purposes such as sealant for containers and watercraft, as glue for fixing arrowheads and spear points to their shafts, as mortar for constructing roads and houses, and as mastic in the manufacture of art objects such as the famous Sumerian "Standard of Ur" (Connan 1999; Wendt and Lu 2006). …