Jonathon E. Ericson

Strontium isotope characterization in the study of prehistoric human ecology

Residence patterns provide keys to social structure, information flow, and patterns of material culture. A biogeochemical model has been formulated—using tooth eruption sequence, elemental exchange rates in bone tissue, and the geochemistry of strontium isotopes—to examine patterns of human residence in the past. Strontium isotopes, characteristic of local geology, pass unmodified through the food chain. isotopic values of human second molar teeth, representative of the individual from ages six to twelve, and bone, representative of the last six years of life, characterize the food chain of pre-marital and marital residences respectively. Marriage residence patterns are determined by stratifying age/sex data. The biogeochemical model and preliminary results are presented for two sites in California.

Skeletal concentrations of lead in ancient Peruvians.

The level of biologic lead (expressed as the ratio of atomic lead to atomic calcium) in bones of Peruvians buried 1600 years ago was found to be 3 x 10(-8), as compared to 2100 to 3500 x 10(-8) in the bones of present-day residents of England and the United States. The ratio of barium to calcium was 2 to 3 x 10(-6) in bones of ancient Peruvians and present-day Americans. Barium and lead have similar morphologic distributions in organisms, so this discrepancy for lead must result from overexposure of present-day people to industrial lead and not from natural variations. The magnitude of this discrepancy has been confirmed by two different lines of investigation not reported in this article. This new evidence suggests that natural interactions of lead in human cells have not yet been determined because reagents, nutrients and controls used in laboratory and field studies have been contaminated with lead far in excess of naturally occurring levels.

Natural skeletal levels of lead in Homo sapiens sapiens uncontaminated by technological lead

Lead, Ba and Ca concentrations were determined in tooth enamel, femur and rib from buried skeletons of PreColumbian Southwest American Indians, 10 subjects who lived 1000 years ago on the Pacific coast at 34 degrees N, and 13 subjects who lived 700 years ago in a desert valley tributary of the Colorado River at 37 degrees N 111 degrees W, both groups living in environments uncontaminated by technological Pb. For the coastal tribe, average Pb/Ca ratios were 1.1 x 10(-7) in enamel, 2.3 x 10(-7) in femur and 4.7 x 10(-7) in rib, while Ba/Ca ratios were 1.2 x 10(-5) in enamel, 32 x 10(-5) in femur and 38 x 10(-5) in rib (wt ratios). For the desert tribe, average Pb/Ca ratios were 4 x 10(-7) in enamel, 11 x 10(-7) in femur and 37 x 10(-7) in rib, while Ba/Ca ratios were 1.1 x 10(-5) in enamel, 7.5 x 10(-5) in femur and 6.2 x 10(-5) in rib. It is shown that biologic levels of Pb and Ba in buried femur and rib at both burial sites and in buried enamel at the Arizona site are obscured by excessive diagenetic additions of Pb and Ba from soil moisture. It is shown that one-third of the Pb in enamel at the Malibu site is biologic, yielding a skeletal Pb/Ca (wt) ratio of 4 x 10(-8). This is equivalent to a mean skeletal concentration of 13 ng Pb g-1 bone ash, and a mean natural body burden of 40 micrograms Pb/70 kg adult Homo sapiens sapiens, uncontaminated by technological Pb. This value is about one-thousandth of the mean body burden of 40 mg industrial Pb/70 kg adult American today, which indicates the probable existence within most Americans of dysfunctions caused by poisoning from chronic, excessive overexposures to industrial Pb.

Lead in ancient human bones and its relevance to historical developments of social problems with lead

Concentrations of metabolic lead in buried ancient bones are obscured by replacement of calcium in apatite by excessive amounts of soil moisture Pb. Concentrations of metabolic barium in bones are affected in a similar way. Added soil Pb and Ba, expressed as log(Pb/Ca) versus log(Ba/Ca) among various bones at a given burial site, are positively covariant, with about 5-fold more soil Pb added for each unit of added soil Ba. The typical natural metabolic Ba/Ca ratio in contemporary people can be measured unambiguously because it as unaffected by industrial pollution. It applies to ancient people because it has not changed historically. The intercept of the covariance curve for buried bones of a given ancient population at the known metabolic Ba/Ca ratio indexes the corresponding metabolic Pb/Ca ratio in bones of that population. Lead levels which prevailed in Romans appear to have been similar to those in contemporary people, which are approximately 1000-fold above natural levels in humans determined by this method in ancient Peruvians. This indicates that studies of natural biochemical reactions in cells free of industrial Pb should be made, because most present biochemical knowledge is founded on data obtained from systems polluted with Pb 1000 to 100000-fold above natural levels. The 5000 year history of smelting Pb by humans indicates that a system of education fostered by genetically common lower brain center functions operated on hundreds of successive generations in a context of cultural changes invoked by feedback from developments in engineering technologies to give rise to the difference between present typical and prehistoric natural levels of Pb in humans. Archaeological and anthropological studies of early developments in writing, music and metallurgy by ancient Peruvians and Persian peoples should be combined with PET-scan studies of their descendants to discover if, as preliminary archaeological data suggest, the two ancient populations differed on a genetic basis in higher brain functions, yet are indistinguishable as metallurgical engineers. This would demonstrate that higher centers of the human brain did not exercise guiding control, through hundreds of generations, over those developments of engineering technologies which resulted in the extreme pollution of the earths biosphere with poisonous Pb.

Heavy Metal in Children’s Tooth Enamel: Related to Autism and Disruptive Behaviors?

To examine possible links between neurotoxicant exposure and neuropsychological disorders and child behavior, relative concentrations of lead, mercury, and manganese were examined in prenatal and postnatal enamel regions of deciduous teeth from children with Autism Spectrum Disorders (ASDs), high levels of disruptive behavior (HDB), and typically developing (TD) children. Using laser ablation inductively coupled plasma mass spectrometry, we found no significant differences in levels of these neurotoxicants for children with ASDs compared with TD children, but there was marginal significance indicating that children with ASDs have lower manganese levels. No significant differences emerged between children with HDB and TD children. The current findings challenge the notion that perinatal heavy metal exposure is a major contributor to the development of ASDs and HDB.

Soil lead concentrations and prevalence of hyperactive behavior among school children in Ottawa, Canada

Abstract This pilot study presents findings of a case study of the prevalence of hyperactive behavior among school children and soil lead concentrations in the urban environment of Ottawa, Canada. Preexisting data on the prevalence of hyperactivity were correlated with soil lead concentrations from soil samples collected in 1981. Soil lead concentrations of the samples were analyzed using atomic absorption spectrometry. Further, synagraphic mapping was done to facilitate spatial analyses of the topographical patterning of the prevalence of hyperactivity and soil lead concentrations. The two major trends in the prevalence of hyperactivity and soil lead data are overlapped and seen as topographical “ridges” running northeast – southwest in the central part of the city. Both trends are geographically bounded and parallel to the major thoroughfares of the city. The explained variability in prevalence of hyperactivity based on soil lead concentrations is 25% in areas of high concordance between the residence of the children and location of the sampling points. The results illustrate the effectiveness of soil lead as a significant indicator of the psychological effect of hyperactivity among urban children, and its importance as a monitor of ambient lead.

Obsidian Hydration Rate Development

Since the seminal work of Friedman and Smith [1] obsidian hydration dating (OHD) has undergone several important stages of development and refinement. This paper will summarize the history of research and developments as to elucidate some areas for future research. Archaeologists have taken a pragmatic and empirical approach towards OHD and hydration rate determination. They would like OHD to become an absolute chronometric technique. Geochemists and material scientists have sought to understand the hydration process from an environmental, chemical and thermodynamic perspective. As suggested by the literature, obsidian hydration appears to be a diffusion, reaction and dissolution process dependent on the chemical and thermal history of the hydration environment. Although there appear to be certain central tendencies, however, there are discrepancies between empirical archaeologically-derived data and theoretical models. California offers a rich data base for synthesis and testing of hydration models. There are over 25 natural obsidian sources many of whose chemical and physical properties have been measured by Ericson [2]. Obsidians have been distributed aboriginally as artifacts into diverse environments. Intensive excavations, underwritten by extensive land development, have contributed to development of a number of source-specific hydration rates for single sources. Reanalysis of the California data warrants future examination to advance our understanding of obsidian hydration dating on a world wide basis.

Hierarchical sampling of multiple strata: an innovative technique in exposure characterization

Sampling of multiple strata, or hierarchical sampling of various exposure sources and activity areas, has been tested and is suggested as a method to sample (or to locate) areas with a high prevalence of elevated blood lead in children. Hierarchical sampling was devised to supplement traditional soil lead sampling of a single stratum, either residential or fixed point source, using a multistep strategy. Blood lead (n=1141) and soil lead (n=378) data collected under the USEPA/UCI Tijuana Lead Project (1996-1999) were analyzed to evaluate the usefulness of sampling soil lead from background sites, schools and parks, point sources, and residences. Results revealed that industrial emissions have been a contributing factor to soil lead contamination in Tijuana. At the regional level, point source soil lead was associated with mean blood lead levels and concurrent high background, and point source soil lead levels were predictive of a high percentage of subjects with blood lead equal to or greater than 10 micro g/dL (pe 10). Significant relationships were observed between mean blood lead level and fixed point source soil lead (r=0.93; P<0.05; R(2)=0.72 using a quadratic model) and between residential soil lead and fixed point source soil lead (r=0.90; P<0.05; R(2)=0.86 using a cubic model). This study suggests that point sources alone are not sufficient for predicting the relative risk of exposure to lead in the urban environment. These findings will be useful in defining regions for targeted or universal soil lead sampling by site type. Point sources have been observed to be predictive of mean blood lead at the regional level; however, this relationship alone was not sufficient to predict pe 10. It is concluded that when apparently undisturbed sites reveal high soil lead levels in addition to local point sources, dispersion of lead is widespread and will be associated with a high prevalence of elevated blood lead in children. Multiple strata sampling was shown to be useful in differentiating among sources by site-specific association to mean blood lead and the prevalence of elevated blood lead at the regional level.