question: If poison is past its expiration date, does it become more poisonous, or less?
comment: That entirely depends on the poison. Some will break down into less toxic compounds, others might break down into more toxic compounds. Or it might do a bit of both. And of course those breakdown products may themselves break down into other things.
passages: New chemical PMNs are submitted early in the chemical’s development so they rarely contain information about chronic toxicity - yet the EPA must respond within the 90-180 day time period after submission of the PMN.
   Chronic poisoning is long-term repeated or continuous exposure to a poison where symptoms do not occur immediately or after each exposure. The patient gradually becomes ill, or becomes ill after a long latent period. Chronic poisoning most commonly occurs following exposure to poisons that bioaccumulate, or are biomagnified, such as mercury, gadolinium, and lead.
  
  Section::::Management.
  
  BULLET::::- Initial management for all poisonings includes ensuring adequate cardiopulmonary function and providing treatment for any symptoms such as seizures, shock, and pain.
   BULLET::::- In some situations elimination of the poison can be enhanced using diuresis, hemodialysis, hemoperfusion, hyperbaric medicine, peritoneal dialysis, exchange transfusion or chelation. However, this may actually worsen the poisoning in some cases, so it should always be verified based on what substances are involved.
  
  Section::::Epidemiology.
  
  In 2010, poisoning resulted in about 180,000 deaths down from 200,000 in 1990. There were approximately 727,500 emergency department visits in the United States involving poisonings—3.3% of all injury-related encounters.
  
  Section::::Applications.
   There are many factors that can increase or decrease the toxicity of toxicants or stressors, making interpretation of test results difficult. These can be chemical, biological, or toxicological.
  
  Section::::Factors that influence toxicity.:Chemical factors.
  
  Water chemistry plays an important role in the toxicity of certain toxicants. This includes pH, salinity, water hardness, conductivity, temperature, and amounts of dissolved organic carbon (DOC)
  
  For instance, the toxicity of copper is decreased with increasing amounts of DOC, as described by the biotic ligand model (BLM).
  
  Section::::Factors that influence toxicity.:Biological factors.
   Since 2011 the NVIC also provides a web-based exposure analysis and poison information system (http://www.vergiftigingen.info]. As with the webPOISONCONTROL system, this is a free-of-charge, fully confidential web application that enables medical professionals to quickly and efficiently assess the potential risks of (mixed) exposures, as well as their clinical signs and symptoms, and possible therapeutic interventions. As with the other online options worldwide, it remains advisable to consult the NVIC if the exposure is to a larger number of substances.
   The risk from toxicity is also distinct from toxicity itself. For instance, the preservative thiomersal used in vaccines is toxic, but the quantity administered in a single shot is negligible.
  
  Section::::History.
   The venom of Agkistrodon contortrix phaeogaster is similar to the venoms produced by other species of the Agkistrodon genus. The exact ratio of toxins to each other varies among species and gender, as does the overall potency of the venom (the ratio of active toxins to other constituents of the venom). The venom is most potent between the late-spring and mid-summer months, this rise in toxicity commences 2–3 weeks prior to reaching peak toxicity. While the initial reduction of potency occurs over approximately one month, the snake's venom remains slightly more toxic throughout the late-summer months until beginning a slow descent to reach its original toxicity by mid-fall.
   However, there is no linear relationship and chemical toxicity is more complex than merely the acute effects caused by short-term exposure. Relatively low doses of contaminants in water, food, and environment can already have significant chronic effects if there is a long-term exposure. Many pollutants, drugs, and natural substances adhere to this principle by causing different effects at different levels, which can as a result lead to health standards that are either too strong or too weak.
  
  Generally the effects of different doses can be very different at different levels (not only bigger and smaller impacts depending on dose). 
   Assignment to a toxicity class is based typically on results of acute toxicity studies such as the determination of values in animal experiments, notably rodents, via oral, inhaled, or external application. The experimental design measures the acute death rate of an agent. The toxicity class generally does not address issues of other potential harm of the agent, such as bioaccumulation, issues of carcinogenicity, teratogenicity, mutagenic effects, or the impact on reproduction.
  
  Regulating agencies may require that packaging of the agent be labeled with a signal word, a specific warning label to indicate the level of toxicity.
  
  Section::::By jurisdiction.
   A poison which enters the food chain—whether of industrial, agricultural, or natural origin—might not be immediately toxic to the first organism that ingests the toxin, but can become further concentrated in predatory organisms further up the food chain, particularly carnivores and omnivores, especially concerning fat soluble poisons which tend to become stored in biological tissue rather than excreted in urine or other water-based effluents. 
   Most biocides, including pesticides, are created to act as acute poisons to target organisms, although acute or less observable chronic poisoning can also occur in non-target organisms (secondary poisoning), including the humans who apply the biocides and other beneficial organisms. For example, the herbicide 2,4-D imitates the action of a plant hormone, which makes its lethal toxicity specific to plants. Indeed, 2,4-D is not a poison, but classified as "harmful" (EU).
   BULLET::::- Predator-prey relationships – either the predator is affected by the toxin resulting in a decline of predator population and thus increasing the prey population; or the prey population is affected by the toxin resulting in a decline in the prey population that, in essence, will cause a decline in the predator population due to lack of food resources
   Biologically speaking, any substance, if given in large enough amounts, is poisonous and can cause death. For instance, several kilograms worth of water would constitute a lethal dose. Many substances used as medications—such as fentanyl—have an only one order of magnitude greater than the ED50. An alternative classification distinguishes between lethal substances that provide a therapeutic value and those that do not.
  
  Section::::Poisoning.
  
  Poisoning can be either acute or chronic, and caused by a variety of natural or synthetic substances. Substances that destroy tissue but do not absorb, such as lye, are classified as corrosives rather than poisons. 
  
  Section::::Poisoning.:Acute.
   Uses for CPTH include killing blackbirds on sprouting rice and on corn and soybean fields. For these and other uses the poison is often given with brown rice. Research continues to improve the effectiveness of delivery on brown rice by causing the poison to be retained on the bait longer and resist degradation by sunlight. The effect of the poison is believed to be cumulative: for example, the LC for starlings was 4.7 ppm over 30 days, but only 1.0 ppm when fed for 90 days.
   The MATC is calculated to protect against chronic effects on overall function or health of an organism, not death. A partial life cycle test must be used. This type of toxicity test uses organisms in their most sensitive life stages, usually during times of early reproduction and growth, but not juveniles. The MATC is the highest concentration that should not cause chronic effects, however, for regulatory purposes, a maximum concentration to protect against acute effects must exist as well.
  
  Section::::Calculation.:Applying MATC to acutely toxic concentrations.
   Section::::Key AAPCC Activities.
  
  BULLET::::- Accreditation of regional poison centers and certification of poison center personnel
  
  BULLET::::- Publication of the annual report of the American Association of Poison Control Centers’ National Poison Data System (NPDS), published every December in "Clinical Toxicology"
  
  BULLET::::- Interaction with private and governmental agencies whose activities influence poisoning and poison centers
  
  BULLET::::- Co-hosting a national conference of poison center leaders that includes scientific presentations, business meetings, and committee meetings
  
  BULLET::::- Development of public and professional education programs and materials
  
  BULLET::::- Collection and analysis of national poisoning data
   2000 mg/kg) to five male and five female rats. The objective is to identify a dose that produces clear signs of toxicity but no mortality (22). Depending on the results of the first test, either no further testing is needed or a higher or lower dose is tested: If mortality occurs, retesting at a lower dose level is necessary (except if the original dose chosen is 5 mg/kg). If no signs of toxicity occur at the initial dose, it is necessary to retest at a higher dose level. The results are thus interpreted in relation to animal survival and evident toxicity (5) and it becomes possible to assign the chemical to one of the OECD classification categories.
   A common method for studying mixtures is to measure the total toxicity of the mixture and consider the internal toxicant interactions as irrelevant. Any mixture effects are taken into account in the total toxicity. The results for this method are limited by being mixture specific and has limited value in determining specific mechanisms of toxicity.
  
  Section::::Limitations.:Alternative ways to study mixtures.:GLM Approach.
   Industry, agriculture, and other sectors employ poisonous substances for reasons other than their toxicity. Most poisonous industrial compounds have associated material safety data sheets and are classed as hazardous substances. Hazardous substances are subject to extensive regulation on production, procurement and use in overlapping domains of occupational safety and health, public health, drinking water quality standards, air pollution and environmental protection. Due to the mechanics of molecular diffusion, many poisonous compounds rapidly diffuse into biological tissues, air, water, or soil on a molecular scale. By the principle of entropy, chemical contamination is typically costly or infeasible to reverse, unless specific chelating agents or micro-filtration processes are available. Chelating agents are often broader in scope than the acute target, and therefore their ingestion necessitates careful medical or veterinarian supervision. 
   Most biocides, including pesticides, are created to act as poisons to target organisms, although acute or less observable chronic poisoning can also occur in non-target organisms (secondary poisoning), including the humans who apply the biocides and other beneficial organisms. For example, the herbicide 2,4-D imitates the action of a plant hormone, which makes its lethal toxicity specific to plants. Indeed, 2,4-D is not a poison, but classified as "harmful" (EU).
   Chronic poisoning is long-term repeated or continuous exposure to a poison where symptoms do not occur immediately or after each exposure. The patient gradually becomes ill, or becomes ill after a long latent period. Chronic poisoning most commonly occurs following exposure to poisons that bioaccumulate, or are biomagnified, such as mercury, gadolinium, and lead.
  
  Contact or absorption of poisons can cause rapid death or impairment. Agents that act on the nervous system can paralyze in seconds or less, and include both biologically derived neurotoxins and so-called nerve gases, which may be synthesized for warfare or industry.
   Chronic toxicity will vary with differences in organisms, including species, size, and age. Certain species are more susceptible to toxic effects, as shown in species sensitivity distributions (SSDs). Certain life stages are more susceptible to adverse effects, which is why early life stage (ELS) toxicity tests are performed for certain aquatic species. In addition, other physical factors, like organism size, can lead to differences in response to toxicants.
  
  Section::::Examples for use in water quality guidelines.
   While poison control centers have traditionally provided expert consultations by telephone, on December 30, 2014 an online option was launched by a group of U.S. poison centers to meet the growing demand for accurate web-based health information. Based on age, weight and substance implicated, it provides case-specific guidance for poison exposures – limited to unintentional, single ingestions of medicines, household products or berries in asymptomatic individuals. The application uses ingredient-based algorithms to generate a recommendation including whether an emergency department visit or call to poison control is required. If it’s safe to stay home, then home treatment recommendations, specific symptoms to expect, and symptoms of greater concern that would require a call to poison control or a visit to an emergency department are outlined. Article 45 of the CLP Regulation places the duty upon Member States to appoint "bodies responsible for receiving information relating to emergency health response". These appointed bodies are often known as Poison Centres.
   Substantial cost savings have been attributed to poison center reductions in unnecessary emergency department (ED) care through accurate assessment and triage of poisoning exposures. The public health and cost benefits from poison center pre-hospital management of patients not needing ED visits favorably impacts the self-pay or copaying general public, the health-care institution supporting the costs of indigent care, the commercial insurance companies and governmental health-care funding agencies. Poison centers assess and manage more than 70 percent of poison exposures over the phone, eliminating the need for callers to seek further medical care. This reduction in medically unnecessary ED visits decreases hospital overcrowding and minimizes unnecessary ambulance runs, freeing critical emergency staff to handle true emergencies more effectively.
   The FDA will issue different levels of recall depending on the severity of the effects. From most to least severe, there is Class I, Class II, and Class III (defined above).There is also market withdrawal which occurs when a drug does not violate FDA regulation but has a known, minor default. The producer must either fix the default or take the drug off the market.
  