Human population

Eye and Skin Contact. Some nickel salts and aqueous solutions of these salts, eg, the sulfate and chloride, may cause a primary irritant reaction of the eye and skin. The most common effect of dermal exposure to nickel is allergic contact dermatitis. Nickel dermatitis may occur in sensitized individuals following close and prolonged contact with nickel-containing solutions or metallic objects such as jewelry, particularly pierced earrings. It is estimated that 8—15% of the female human population and 0.2—2% of the male human population is nickel-sensitized (125). 

Dose—response evaluation is used in describing the quantitative relationship between the amount of exposure to a substance and the extent of toxic injury or disease. Data may be derived from animal studies or from studies in exposed human populations. Dose—response toxicity relationship for a substance varies under different exposure conditions. The risk of a substance can not be ascertained with any degree of confidence unless... 

Ha2ard is the likelihood that the known toxicity of a material will be exhibited under specific conditions of use. It follows that the toxicity of a material, ie, its potential to produce injury, is but one of many considerations to be taken into account in assessment procedures with respect to defining ha2ard. The following are equally important factors that need to be considered physicochemical properties of the material use pattern of the material and characteristics of the environment where the material is handled source of exposure, normal and accidental control measures used to regulate exposure the duration, magnitude, and frequency of exposure route of exposure and physical nature of exposure conditions, eg, gas, aerosol, or Hquid population exposed and variabiUty in exposure conditions and experience with exposed human populations. 

The goal of any statistical analysis is inference concerning whether on the basis of available data, some hypothesis about the natural world is true. The hypothesis may consist of the value of some parameter or parameters, such as a physical constant or the exact proportion of an allelic variant in a human population, or the hypothesis may be a qualitative statement, such as This protein adopts an a/p barrel fold or I am currently in Philadelphia. The parameters or hypothesis can be unobservable or as yet unobserved. How the data arise from the parameters is called the model for the system under study and may include estimates of experimental error as well as our best understanding of the physical process of the system. 

The field of statistics as a separate discipline began m the early to mid nineteenth century among German, British, French, and Belgian social reformers, refeired to as statists i.e., those that were concerned with numbers related to the state, including crime rates, income distributions, etc. [34] The appeal of frequency-based interpretation of probability would have been natural m the study of large human populations. 

In risk characterization, step four, the human exposure situation is compared to the toxicity data from animal studies, and often a safety -margin approach is utilized. The safety margin is based on a knowledge of uncertainties and individual variation in sensitivity of animals and humans to the effects of chemical compounds. Usually one assumes that humans are more sensitive than experimental animals to the effects of chemicals. For this reason, a safety margin is often used. This margin contains two factors, differences in biotransformation within a species (human), usually 10, and differences in the sensitivity between species (e.g., rat vs. human), usually also 10. The safety factor which takes into consideration interindividual differences within the human population predominately indicates differences in biotransformation, but sensitivity to effects of chemicals is also taken into consideration (e.g., safety faaor of 4 for biotransformation and 2.5 for sensitivity 4 x 2.5 = 10). For example, if the lowest dose that does not cause any toxicity to rodents, rats, or mice, i.e., the no-ob-servable-adverse-effect level (NOAEL) is 100 mg/kg, this dose is divided by the safety factor of 100. The safe dose level for humans would be then 1 mg/kg. Occasionally, a NOAEL is not found, and one has to use the lowest-observable-adverse-effect level (LOAEL) in safety assessment. In this situation, often an additional un-... 

Provides information on how levels of exposure of hazardous chemicals affect human health. Covers levels of exposure to hazardous chemicals below which no adverse health effects are expected to occur in various segments of the human population. The reference dose and carcinogenicity assessments on IRIS can sen>e as guides in e >aluating potential health hazards and selecting response to alleviate a potential risk to human health. Hours 8 00 a.m. to 4 40 p.m. EST, Monday - Friday. 

Generally, the main pathways of exposure considered in tliis step are atmospheric surface and groundwater transport, ingestion of toxic materials that luu c passed tlu-ough the aquatic and tcncstrial food chain, and dermal absorption. Once an exposure assessment determines the quantity of a chemical with which human populations nniy come in contact, the information can be combined with toxicity data (from the hazard identification process) to estimate potential health risks." The primary purpose of an exposure assessment is to... 

The questionable validity if animal studies and short-term tests with respect to the prediction of long-term, adverse liealUi impacts in a human population... 

E.xposure assessment is tire detennination of tire magnitude, frequency, duration, and routes of exposure to human populations and ecosystems. 

Developmental Refei-ence Dose (RfDji) An estimate (with an uncertainty spanning perhaps an order of magnitude or greater) of an exposure level for the human population, including sensitive subpopulations, that is likely to be without an appreciable risk of developmental effects. Developmental RfDs are used to evaluate the effects of a single exposure event. 

Using dose-response information from homogeneous animal populations or healthy human populations to predict the effects likely to be observed in the general population consisting of individuals with a wide range of sensitivities... 

RfD, the Reference Dose, is an estimate of a daily e.xposure level for the human population that will not produce an adverse effect. 

Epidemiology is a discipline within the health sciences that deals with the study of the occurrence of disease in human populations. Epidemiologists arc generally concerned with groups of people who share certain characteristics. 

The natural supply of nitrogen available to plants from the nitrogen cycle is limited. To meet the growing demands for agriculture crops, nitrogen is added to soil in the form of fertilizers. An estimated one-third of the human population is fed as a result of the use of synthetic fertilizers. 

Urinary lithiasis is a disease in which calculi form in the kidney and urinary tract. Roughly 5 % of the human population suffers to some degree from urinary lithiasis. A number of severely afflicted patients (e.g. ca. 60,000 in West Germany and more than 100,000 in the U.S.) are hospitalized yearly for major surgical treatment. Obviously, nephrolithiasis is not only a common ailment but also an issue of great social and economic consequence. 

Infection with the obligatory intracellular parasite T. gondii is mainly acquired by ingestion of contaminated food or water. Approximately a third of the world s human population is infected. 

---