Earth Materials and Health Research Priorities for Earth Science and Public Health (2007) / Chapter Skim
Currently Skimming:
2 Earth Processes and Human Physiology
2 Earth Processes and Human Physiology
Pages 15-40
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 15... ...
However, natural background properties and earth processes such as volcanic eruptions, as well as human activities involving the extraction, refining, and manufacturing of mineral commodities, have led to unwanted side effects such as environmental degradation and health hazards. Among the latter are airborne dusts and gases, chemical pollutants in agricultural, industrial, and residential waters, and toxic chemical species in foodstuffs and manufactured products.
|
From page 16... ...
This is followed by a brief description of those aspects of human physiology that are -- through their responses to bioaccessible nutrients and hazardous materials -- directly responsive to the biogeochemical environment. EARTH PROCESSES The near-surface portions of the planet and their complex couplings with -- and feedbacks from -- the atmosphere, hydrosphere, and biosphere make up the interactive earth systems so crucial for life.
|
From page 17... ...
In addition to the direct fatalities and injuries, natural catastrophes result in the displacement of surviving populations into unhealthy environments where communicable diseases can -- and often do -- spread widely. Plate Tectonics -- Origins of Continental and Ocean Crust Scientists have studied the on-land geology of the earth for more than two centuries, and much is known concerning the diverse origins of the continental crust, its structure, and constituent rocks and minerals (see Earth Materials below)
|
From page 18... ...
18 EARTH MATERIALS AND HEALTH FIGURE 2.1 Schematic cross-section of a mid-oceanic ridge spreading center (a divergent plate boundary)
|
From page 19... ...
19 EARTH PROCESSES AND HUMAN PHYSIOLOGY An oceanic plate moves away from the ridge axis until it reaches a convergent plate boundary. Here, one slab must return to the mantle to conserve volume -- the process of subduction (see Figure 2.2)
|
From page 20... ...
This is also the region where plate convergence and contraction builds structural mountain belts, resulting in crustal thickening, rugged topography, and high erosion rates -- such belts are characterized by landslides, mudflows, and other mass movements. Earth Materials The earth's crust constitutes far less than 1 percent of the entire planetary mass but represents the nurturing substrate for virtually all life on
|
From page 21... ...
To investigate and quantify the human health and longevity effects due to the presence and bioassimilation of earth materials, we need to understand the nature of the constituents that make up the earth's crust -- minerals and rocks. A mineral is a naturally occurring, inorganically produced solid that possesses a characteristic chemistry or limited range of compositions, and a periodic, three-dimensional atomic order or polymerization (i.e., crystal structure)
|
From page 22... ...
It is such weathering products that in many cases provide the ready supply of both nutrients and toxic chemical species that influence the existence of life in general and human health in particular. Geological mapping and remote sensing techniques provide the enhanced spatial understanding of the areal disposition and concentration of surficial earth materials that are an essential component of epidemiological investigations of environmentally related diseases and human senescence.
|
From page 23... ...
Soil also plays a critical public health role in regard to pollutants that have been disposed of at the earth's surface, as they can promote or restrict transport to groundwater, the atmosphere, or food crops. Soil is a complex mixture of weathered rock particles, organic residues, air, water, and billions of living organisms that are the end product of the interaction of the parent rock material with climate, living organisms, topography, and time -- the five soil-forming factors.
|
From page 24... ...
In addition, clay particles are the primary soil particles that have an associated electric charge. This is the basis for a soils cation-exchange capacity (CEC)
|
From page 25... ...
Elemental variations result both from the mineralogical and geochemical characteristics inherited from parent rock materials and, particularly for the clay fraction, from macro and trace elements introduced by contamination. The distribution of inorganic and organic constituents among the different soil particle classes is summarized in Table 2.1.
|
From page 26... ...
Pore space also regulates water movement and retention as well as air diffusion and microsite redox potentials. Organic Matter in Soils Organic compounds are incorporated into soil at the surface via plant residues such as leaves or grassy material.
|
From page 27... ...
In contrast, sandy soils have larger pore sizes, allowing more rapid water and air movement. Aerobic soil microbes require both water and oxygen, which are both found within the pore space, and therefore soil moisture content controls the amount of available oxygen in a soil.
|
From page 28... ...
These in turn define the directions and magnitudes of the physical and biological changes that provide the context for modern conditions. This section notes the diversity of biological systems, emphasizing the metabolic processes of microorganisms and their roles in consuming earth materials to produce metabolites and influence the environment.
|
From page 29... ...
The loss of body structural integrity and function can occur when homeostasis is perturbed by internal factors or by physiological response to hazardous materials in the environment. Most earth materials -- solids, liquids, or gases -- are essential for the body or are benign.
|
From page 30... ...
These tiny balloonlike structures are surrounded by arterioles and venules where the essential gas exchange -- into and from the blood -- actually takes place. Hazardous materials in ambient air may access the inner portions of the body through the respiratory system sampled with each breath.
|
From page 31... ...
31 EARTH PROCESSES AND HUMAN PHYSIOLOGY FIGURE 2.4 Schematic diagram of the human respiratory system, showing the gross anatomy of the lung, the covering membranes (pleura) , airways, and air sacs (alveoli)
|
From page 32... ...
For example, the relative risk for lung cancer among pack-a-day lifetime smokers is about 15, meaning that smokers have about 15 times the rate of lung cancer as people who have never smoked. There is a gradient of risk in most real world situations, with the relative risk increasing with the level of expo sure.
|
From page 33... ...
in an epidemio logical study of bladder cancer in northern New England, which also includes collaborators from Dartmouth Medical School and the state health departments of Vermont, New Hampshire, and Maine. Since 1950, blad der cancer mortality in New England for both males and females has been above the U.S.
|
From page 34... ...
, to the specialized cells for transport of gases and those that act in natural defense of the system, have a multitude of normal biological reactions. Some may become pathological and disadvantageous, decreasing the availability of oxygen.
|
From page 35... ...
The tract is effectively a flexible tube that ranges in length up to about 9 m from the mouth to the anus in an adult. The organs in the digestive tract are supported by fibrous connective tissue, and in some parts of the system there are double layers that also 1Inhaled particulate material enters the nose, throat, and upper respiratory tract, whereas respirable particulate material is able to penetrate deep into the lungs.
|
From page 36... ...
Ingestion of hazardous materials or elements in food or water may induce local aberrations in the normal operations of each of these essential organs. High concentrations of arsenic (see Chapters 4 and 5)
|
From page 37... ...
For earth science materials and the human body, bioavailable concentrations are always less than total elemental concentrations. Many trace elements are metabolic requirements for humans, so too small an amount of these elements will result in deficiency (see Figure 2.5A)
|
From page 38... ...
In recent years, considerable interest has been focused on assessing the human health risk posed by metals, metalloids, and trace elements in the environment. It has long been recognized that large areas of the globe contain human populations characterized by having trace element excess, deficiency, or chronic poisoning (e.g., Selinus et al., 2005)
|
From page 39... ...
39 EARTH PROCESSES AND HUMAN PHYSIOLOGY Benefit A LOAEL threshold NOAEL Deficient Normal Toxic Lethal Harm Essential Elements Response ? Normal Toxic Lethal Harm Nonessential Elements B Concentration (or dose)
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.