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Lecture

Chapter 10.doc


Department
Geography
Course Code
GGR374H1
Professor
oldsten

Page:
of 3
Chapter 10: Body Burdens of Industrial Chemicals in the General Population:
Petroleum and other materials are transformed by industrial processes into fuels,
plastic, pesticides, cosmetics, food additives and pharmaceuticals
Residues of human made substance can now be found in the air, soil, water and
food web in the most remote reaches of the plant.
Pollutants that are distributed ubiquitously result in universal human exposure
through inhalation, drinking water, and the food supply.
Some of the substances to which the general human population is exposed resist
metabolism and excretion and therefore accumulate in body tissues.
The quantity of an exogenous substance or its metabolites that has accumulated in
an individual or population is defined as a body burden.
Body-burden estimation:
Individual’s body burden of a pollutant is estimated by measuring the concentration
of that substance in one or more tissues, usually by gas chromatography/mass
spectrometry.
Chemical body burdens are complex and dynamic in a number of ways, and these
characteristics make a full characterization of the general public body burden
exceedingly difficulty.
First the body of burden of a pollutant is not stable over time. It reflects a dynamic
balance between the amount of taken in and the amount excreted or metabolized
into another material
Second, body burdens are not distributed homogenously within an individual: the
partitioning of a pollutant among various tissues and fluids reflects the substances
degradability and affinity for fats, minerals and other endogenous materials.
The choice of compartment in biomonitoring for any pollutants will affect the level
of measured, the limit of detection and the recency of exposure being estimated.
Third, the body of burden of an individual in todays environment consist of
hundred of syntehic substances.
Biomonitoring programs in the United States:
Public health officials and scientists use biomonitoring information for surveillance,
control and treatment
The purpose of many biomonitoring programs has been to assess the health risks of
occupationally or environmentally exposed individuals.
Three biomonitoring surveys have studied broad samples of the U.S population.
The NHATS programs has been criticized for lacking a standardized methodology
and using a sample of individuals that may not accurately reflect the nation
populations, but the programs results remain one of the most comprehensive
available data sets on the general populations body burden.
A reference range is defined as the concentration of a particular substance that is
excepted to be present in the genral population with no unusal chemical exposure.
The reference range is the standard against which a measuring laboratory can say
that results for any group or indivudal are high in a normal range or low.
Organochlorine substance:
Organochlorine are a class of carbon based chemicals that contain one or more
chlirone atoms.
Thousands of additional organochlorines are formed as a by-products in the
manufacture, some uses and disposal of organochrline containin product.
Three characteristics of organochlorines make them particularly troublesome. First
chloringation changes the chemical stability of organic chemicals in largly
predictable ways, making many organcholrines highly persistent in the
environment.
Second, many organochlirones are strongly lipophilic—that is they are highly
soluble in fats but not in water, so they accumulate in fatty tissues.
Chlorination almost invariably increase the solulbility of organic substances in fat
and reduces their water solubility, the increase in lipophhiia become greater with
each chlorine atom added to the molecule.
Finally organochlirines tend to be considerably more toxic and more carcinogenic
than their nonchrliroinated analogues.
Some organchlorine chemicals produce a variety of adverse health impacts,
including cancer, organ damage, and reproductive, neurological and immunological
toxicity, mostly in the sentence period of fetal infant development.
Normal body burdens:
Hydrocarbon solvents are commonly found in fat and blood with toluene and
xylene detected in 100 percent of NHANES III
Body-burden variation:
Age:
Tissue concentration of industrial chemicals that bioaccumulation are expected to
increase with age.
Gender:
Sex differences in pollutant exposure and pharmacokinetics that may affect
pollutant accumulation have not been well studied.
Geography:
Although industrial chemicals are ubiquitous, location affects the magnitude of
exposure.
Local pollutants source can cause increased exposures.
Surveys of pesticide exposure suggest that residents of rural agricultural
communities have higher body burdens than urban residents.
Race:
Blood-lead levels have been consistently found to be higher In African Americans
than in whites.
Occupations:
There are ample data to confirm that persons will occupational exposures have
higher body burdens of industrial chemicals than person’s without such
occupational exposures, chemical and agricultural workers being the obvious
examples.
Time trends:
Many studies confirm that concentrations of organochlorine chemicals that were
restricted in the United stats and Canada.
Critical populations: women and children:
Women, however excrete accumulated persistent chemicals into the fat of breast
milk and in small quantities.
One function of the placenta is to serve as a barrier to keep harmful substance from
the embryo and fetus, but fat soluble organocholins cross the placenta readily.
Public Health and Epideiological significance:
The measurement of body burden provides an assessment of an individuals long
term exposure to a chemical, a critical parameter in epidemiologiclogy and risk
assessment
Bdoy burden measurements automatically account for differences between species
in metabolism and execration, increasing confidence in interspecies and
interindivudal estimates of toxicity.
The xenobiotic body burden is biologically important because it provides a
reservoir for continous internal exposure to these substances.
Measruments of body burdens also provides an important means to study the
relation between universal chemical exposure and adverse health outcomes.
Body burdens provide a present indicator of long term exposure, and analyses can
target an individual substance in the human population can be compared to those
that produce adverse health impacts in more easily studied lab animals.
Health effects as background exposures:
A study found that prenatal PCB exposure, determined as the burden of total PCBs
in the mothers plasma was related to lower birth weight, lower growth rate, lower
psychomotor.
Maternal PCB levels are strongly correlated with the incidence of low birth weight
among children born to women who eats fish with Baltic sea.
The risk of newborn hemorrhagic disease has been linked to dioxin levels in the
breast of milk of mothers from the general Dutch population.
A number of linked between breast and haematopoietic cancers and the body
burden of PCBs or specific organochlorine pesticides, although other studies have
not corroborated these results.
Finally maternal body burden of PCBs and dioxin are associated with reduced
thyroid hormone levels in dutcuh
Maternal body of burdens of PCBs and dioxin are associated with reduced thyroid
hormone levels in dutch infants
Public understanding of Body-burden Data:
Body burden measurements can play an important role in risk communication and
provide workers and citizens with knowledge of their personal exposures.