Chemical latency period

For less well defined incidents however, these detection systems may be inadequate. Portable chemical detectors may not be able to be deployed to the site, not detect the agen, or give inconclusive results. Clinical findings may be non-specific, present in an atypical manner, or for example in the case of sulphur mustard, have a latency period that delays firm pattern recognition. Due to the physico-chemical properties of the agent or the time between release and collection, environmental samples may have low agent levels or sufficiently high contaminants to prevent adequate results. 

First, one could observe that in the 2-1/2 years that the PMN program has been in effect there have been no known cases of people dropping dead because of a new chemical. This is not a very informative observation, however, because it is more a comment on the long latency period of chronic effects and our inability to detect chemical problems than it is an observation about the lack of problems with new chemicals. This is not to say that chemicals with adverse effects have gone through the PMN process—only that we would not know it if they had. 

For short-term experiments, thorium-232 is considered radiologically inert since its half-life is so long. Therefore, the chemical toxicity of thorium was tested using this isotope. The low chemical toxicity of thorium was evidenced by the lack of initial systemic effects in patients injected with Thorotrast and in occupationally exposed workers. Animal studies also showed low toxicity (Guimaraes et al. 1955 Patrick and Cross 1948). Natural thorium (thorium-232) is toxic only after a latency period of 20-30 years, when the radiological effects are manifested. 

Most substances classified as epigenetic carcinogens are promoters that act after initiation. Manifestations of promotion include increased numbers of tumor cells and decreased length of time for tumors to develop (shortened latency period). Promoters do not initiate cancer, are not electrophilic, and do not bind with DNA. The classic example of a promotor is a substance known chemically as decanoyl phorbol acetate or phorbol myristate acetate, a substance extracted from croton oil. 

At an ecosystem level, complex interactions within and between populations and nonlinear biological dynamics may create a latency period between the exposure event and certain effects (Landis et al. 1996 Matthews et al. 1996), particularly when considering the indirect effects of chemical stress. Populations of organisms may be affected by toxicants in an indirect way when a reduction or elimination... 

The consequences of chemical disruption of the development of the endocrine system or of endocrine function during early life have only begun to be explored (Damstra et al., 2002 Dietert et al., 2002). Importantly, exposures during gestation or childhood may not manifest immediately. In some cases, the latency period between... 

Chronic toxicity studies provide information on the long-term health effects of chemical substances. Adverse health effects in exposed animals and subsequent severe damage are known to occur after repeated exposure to low doses over a period of time. The slow accumulation of mercury or lead in the body or after a long latency period from exposure to chemical carcinogens is an example. Chronic or prolonged periods of exposure to chemical substances may also cause adverse effects on the reproduction and behavior of animals and humans. The symptoms caused after chronic exposure usually differ from those observed in acute poisoning from the same chemical. In fact, when exposed to low concentrations of chemical substances, as is the case with chronic toxicity studies, the industrial worker and common public are unaware of the exposure. 

Latency period The period of time between exposure to something that causes a disease and the onset of the health effect. Cancer caused by exposure to chemical substances may have a latency period of 5-40 years LDH Lactate dehydrogenase... 

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