The signs and symptoms are generally flu-like. They include fever, chills, nausea, headache, fatigue, muscle aches, joint pains, lack of appetite, shortness of breath, pneumonia, chest pain, change in blood pressure, and coughing. A sweet or metallic taste in the mouth may also be reported, along with a dry or irritated throat which may lead to hoarseness. Symptoms of a more severe metal toxicity may also include a burning sensation in the body, shock, no urine output, collapse, convulsions, shortness of breath, yellow eyes or yellow skin, rash, vomiting, watery or bloody diarrhea or low or high blood pressure, which require prompt medical attention. Flu-like symptoms normally disappear within 24 to 48 hours. Full recovery often requires one to three weeks.

Health effects of pesticides may be acute or delayed in those who are exposed. A 2007 systematic review found that "most studies on non-Hodgkin lymphoma and leukemia showed positive associations with pesticide exposure" and thus concluded that cosmetic use of pesticides should be decreased. Strong evidence also exists for other negative outcomes from pesticide exposure including neurological problems, birth defects, fetal death, and neurodevelopmental disorder.

According to The Stockholm Convention on Persistent Organic Pollutants, 9 of the 12 most dangerous and persistent chemicals are pesticides.

A pesticide poisoning occurs when chemicals intended to control a pest affect non-target organisms such as humans, wildlife, or bees. There are three types of pesticide poisoning. The first of the three is a single and short-term very high level of exposure which can be experienced by individuals who commit suicide, as well as pesticide formulators. The second type of poisoning is long-term high-level exposure, which can occur in pesticide formulators and manufacturers. The third type of poisoning is a long-term low-level exposure, which individuals are exposed to from sources such as pesticide residues in food as well as contact with pesticide residues in the air, water, soil, sediment, food materials, plants and animals.

In developing countries, such as Sri Lanka, pesticide poisonings from short-term very high level of exposure (acute poisoning) is the most worrisome type of poisoning. However, in developed countries, such as Canada, it is the complete opposite: acute pesticide poisoning is controlled, thus making the main issue long-term low-level exposure of pesticides.

Metal fume fever, also known as brass founders' ague, brass shakes, zinc shakes, galvie flu, metal dust fever, Welding Shivers, or Monday morning fever, is an illness primarily caused by exposure to chemicals such as zinc oxide (ZnO), aluminum oxide (AlO), or magnesium oxide (MgO) which are produced as byproducts in the fumes that result when certain metals are heated. Other common sources are fuming silver, gold, platinum, chromium (from stainless steel), nickel, arsenic, manganese, beryllium, cadmium, cobalt, lead, selenium, and zinc.

Welders are commonly exposed to the substances that cause metal fume fever from the base metal, plating, or filler. Brazing and soldering can also cause metal poisoning due to exposure to lead, zinc, copper, or cadmium. In extreme cases, cadmium (present in some older silver solder alloys) can cause loss of consciousness.

People may be exposed to toxic chemicals or similar dangerous substances from pharmaceutical products, consumer products, the environment, or in the home or at work. Many toxic tort cases arise either from the use of medications, or through exposure at work.

A toxic tort claim is a specific type of personal injury lawsuit in which the plaintiff claims that exposure to a chemical or dangerous substance caused the plaintiff's injury or disease.

The symptoms of organophosphate poisoning include muscle weakness, fatigue, muscle cramps, fasciculation, and paralysis. Other symptoms include hypertension, and hypoglycemia.

Overstimulation of nicotinic acetylcholine receptors in the central nervous system, due to accumulation of ACh, results in anxiety, headache, convulsions, ataxia, depression of respiration and circulation, tremor, general weakness, and potentially coma. When there is expression of muscarinic overstimulation due to excess acetylcholine at muscarinic acetylcholine receptors symptoms of visual disturbances, tightness in chest, wheezing due to bronchoconstriction, increased bronchial secretions, increased salivation, lacrimation, sweating, peristalsis, and urination can occur.

The effects of organophosphate poisoning on muscarinic receptors are recalled using the mnemonic SLUDGEM (salivation, lacrimation, urination, defecation, gastrointestinal motility, emesis, miosis) An additional mnemonic is MUDDLES: miosis, urination, diarrhea, diaphoresis, lacrimation, excitation, and salivation.

The onset and severity of symptoms, whether acute or chronic, depends upon the specific chemical, the route of exposure (skin, lungs, or GI tract), the dose, and the individuals ability to degrade the compound, which the PON1 enzyme level will affect.

Most pesticide-related illnesses have signs and symptoms that are similar to common medical conditions, so a complete and detailed environmental and occupational history is essential for correctly diagnosing a pesticide poisoning. A few additional screening questions about the patient's work and home environment, in addition to a typical health questionnaire, can indicate whether there was a potential pesticide poisoning.

If one is regularly using carbamate and organophosphate pesticides, it is important to obtain a baseline cholinesterase test. Cholinesterase is an important enzyme of the nervous system, and these chemical groups kill pests and potentially injure or kill humans by inhibiting cholinesterase. If one has had a baseline test and later suspects a poisoning, one can identify the extent of the problem by comparison of the current cholinesterase level with the baseline level.

Acute health problems may occur in workers that handle pesticides, such as abdominal pain, dizziness, headaches, nausea, vomiting, as well as skin and eye problems. In China, an estimated half million people are poisoned by pesticides each year, 500 of whom die. Pyrethrins, insecticides commonly used in common bug killers, can cause a potentially deadly condition if breathed in.

Neurotoxic effects have also been linked to poisoning with OP pesticides causing four neurotoxic effects in humans: cholinergic syndrome, intermediate syndrome, organophosphate-induced delayed polyneuropathy (OPIDP), and chronic organophosphate-induced neuropsychiatric disorder (COPIND). These syndromes result after acute and chronic exposure to OP pesticides.

Cholinergic syndrome occurs in acute poisonings with OP pesticides and is directly related to levels of AChE activity. Symptoms include miosis, sweating, lacrimation, gastrointestinal symptoms, respiratory difficulties, shortness of breath, slowed heart rate, cyanosis, vomiting, diarrhea, trouble sleeping, as well as other symptoms. Along with these central effects can be seen and finally seizures, convulsions, coma, respiratory failure. If the person survives the first day of poisoning personality changes can occur, aggressive events, psychotic episodes, disturbances and deficits in memory and attention, as well as other delayed effects. When death occurs, it is most commonly due to respiratory failure from the combination of central and peripheral effects, paralysis of respiratory muscles and depression of the brain respiratory center. For people afflicted with cholinergic syndrome, atropine sulfate combined with an oxime is used to combat the effects of the acute OP poisoning. Diazepam is sometimes also administered in combination with the atropine and oximes.

The intermediate syndrome (IMS) appears in the interval between the end of the cholinergic crisis and the onset of OPIDP. Symptoms associated with IMS manifest within 24–96 hours after exposure. The exact etiology, incidence, and risk factors associated with IMS are not clearly understood, but IMS is recognized as a disorder of neuromuscular junctions. IMS occurs when a person has a prolonged and severe inhibition of AChE and has been linked to specific OP pesticides such as methylparathion, dichlorvos, and parathion. Patients present with increasing weakness of facial, neck flexor and respiratory muscles.

OPIDP occurs in a small percentage of cases, roughly two weeks after exposure, where temporary paralysis occurs. This loss of function and ataxia of peripheral nerves and spinal cord is the phenomenon of OPIDP. Once the symptoms begin with shooting pains in both legs, the symptoms continue to worsen for 3–6 months. In the most severe cases quadriplegia has been observed. Treatment only affects sensory nerves, not motor neurons which may permanently lose function. The aging and phosphorylation of more than 70% of functional NTE in peripheral nerves is one of the processes involved in OPIDP. Standard treatments for OP poisoning are ineffective for OPIDP.

COPIND occurs without cholinergic symptoms and is not dependent on AChE inhibition. COPIND appears with a delay and is long lasting. Symptoms associated with COPIND include cognitive deficit, mood change, autonomic dysfunction, peripheral neuropathy, and extrapyramidal symptoms. The underlying mechanisms of COPIND have not been determined, but it is hypothesized that withdrawal of OP pesticides after chronic exposure or acute exposure could be a factor.

Common symptoms of mercury poisoning include peripheral neuropathy, presenting as paresthesia or itching, burning, pain, or even a sensation that resembles small insects crawling on or under the skin (formication); skin discoloration (pink cheeks, fingertips and toes); swelling; and desquamation (shedding or peeling of skin).

Mercury irreversibly inhibits selenium-dependent enzymes (see below) and may also inactivate "S"-adenosyl-methionine, which is necessary for catecholamine catabolism by catechol-"O"-methyl transferase. Due to the body's inability to degrade catecholamines (e.g. epinephrine), a person suffering from mercury poisoning may experience profuse sweating, tachycardia (persistently faster-than-normal heart beat), increased salivation, and hypertension (high blood pressure).

Affected children may show red cheeks, nose and lips, loss of hair, teeth, and nails, transient rashes, hypotonia (muscle weakness), and increased sensitivity to light. Other symptoms may include kidney dysfunction (e.g. Fanconi syndrome) or neuropsychiatric symptoms such as emotional lability, memory impairment, or insomnia.

Thus, the clinical presentation may resemble pheochromocytoma or Kawasaki disease. Desquamation (skin peeling) can occur with severe mercury poisoning acquired by handling elemental mercury.

Beryllium poisoning is poisoning by the toxic effects of beryllium, or more usually its compounds. It takes two forms:

- Acute beryllium poisoning, usually as a result of exposure to soluble beryllium salts

- Chronic beryllium disease (CBD) or berylliosis, usually as a result of long-term exposure to beryllium oxide usually caused by inhalation.

Classically acute radiation syndrome is divided into three main presentations: hematopoietic, gastrointestinal, and neurological/vascular. These syndromes may or may not be preceded by a prodrome. The speed of onset of symptoms is related to radiation exposure, with greater doses resulting in a shorter delay in symptom onset. These presentations presume whole-body exposure and many of them are markers which are not valid if the entire body has not been exposed. Each syndrome requires that the tissue showing the syndrome itself be exposed. The hematopoietic syndrome requires exposure of the areas of bone marrow actively forming blood elements (i.e., the pelvis and sternum in adults). The neurovascular symptoms require exposure of the brain. The gastrointestinal syndrome is not seen if the stomach and intestines are not exposed to radiation. Some areas affected are:

1. Hematopoietic. This syndrome is marked by a drop in the number of blood cells, called aplastic anemia. This may result in infections due to a low amount of white blood cells, bleeding due to a lack of platelets, and anemia due to few red blood cells in the circulation. These changes can be detected by blood tests after receiving a whole-body acute dose as low as 0.25 Gy, though they might never be felt by the patient if the dose is below 1 Gy. Conventional trauma and burns resulting from a bomb blast are complicated by the poor wound healing caused by hematopoietic syndrome, increasing mortality.

2. Gastrointestinal. This syndrome often follows absorbed doses of 6–30 Gy (600–3000 rad). The signs and symptoms of this form of radiation injury include nausea, vomiting, loss of appetite, and abdominal pain. Vomiting in this time-frame is a marker for whole body exposures that are in the fatal range above 4 Gy. Without exotic treatment such as bone marrow transplant, death with this dose is common. The death is generally more due to infection than gastrointestinal dysfunction.

3. Neurovascular. This syndrome typically occurs at absorbed doses greater than 30 Gy (3000 rad), though it may occur at 10 Gy (1000 rad). It presents with neurological symptoms such as dizziness, headache, or decreased level of consciousness, occurring within minutes to a few hours, and with an absence of vomiting. It is invariably fatal.

The prodrome (early symptoms) of ARS typically includes nausea and vomiting, headaches, fatigue, fever, and a short period of skin reddening. These symptoms may occur at radiation doses as low as 0.35 Gy (35 rad). These symptoms are common to many illnesses, and may not, by themselves, indicate acute radiation sickness.

Mercury poisoning is a type of metal poisoning due to mercury exposure. Symptoms depend upon the type, dose, method, and duration of exposure. They may include muscle weakness, poor coordination, numbness in the hands and feet, skin rashes, anxiety, memory problems, trouble speaking, trouble hearing, or trouble seeing. High level exposure to methylmercury is known as Minamata disease. Methylmercury exposure in children may result in acrodynia (pink's disease) in which the skin becomes pink and peels. Long-term complications may include kidney problems and decreased intelligence. The effects of long-term low-dose exposure to methylmercury is unclear.

Forms of mercury exposure include metal, vapor, salt, and organic compound. Most exposure is from eating fish, amalgam based dental fillings, or exposure at work. In fish, those higher up in the food chain generally have higher levels of mercury. Less commonly poisoning may occur as an attempt to end one's life. Human activities that release mercury into the environment include the burning of coal and mining of gold. Tests of the blood, urine, and hair for mercury are available but do not relate well to the amount in the body.

Prevention includes eating a diet low in mercury, removing mercury from medical and other devices, proper disposal of mercury, and not mining further mercury. In those with acute poisoning from inorganic mercury salts, chelation with either dimercaptosuccinic acid (DMSA) or dimercaptopropane sulfonate (DMPS) appears to improve outcomes if given within a few hours of exposure. Chelation for those with long-term exposure is of unclear benefit. In certain communities that survive on fishing, rates of mercury poisoning among children have been as high as 1.7 per 100.

Argyria or argyrosis is a condition caused by excessive exposure to chemical compounds of the element silver, or to silver dust. The most dramatic symptom of argyria is that the skin turns purple or purple-grey. It may take the form of "generalized argyria" or "local argyria". Generalized argyria affects large areas over much of the visible surface of the body. Local argyria shows in limited regions of the body, such as patches of skin, parts of the mucous membrane or the conjunctiva.

The terms argyria and argyrosis have long been used interchangeably, with argyria being used more frequently. Argyrosis has been used particularly in referring to argyria of the conjunctiva, but the usage has never been consistent and cannot be relied on except where it has been explicitly specified. The term is from "argyros" silver.

Poisoning is a condition or a process in which an organism becomes chemically harmed (poisoned) by a toxic substance or venom of an animal.

Acute poisoning is exposure to a poison on one occasion or during a short period of time. Symptoms develop in close relation to the degree of exposure. Absorption of a poison is necessary for systemic poisoning (that is, in the blood throughout the body). In contrast, substances that destroy tissue but do not absorb, such as lye, are classified as corrosives rather than poisons. Furthermore, many common household medications are not labeled with skull and crossbones, although they can cause severe illness or even death. In the medical sense, toxicity and poisoning can be caused by less dangerous substances than those legally classified as a poison. Toxicology is the study and practice of the symptoms, mechanisms, diagnosis, and treatment of poisoning.

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.

Inhaled or ingested cyanide, used as a method of execution in gas chambers, almost instantly starves the body of energy by inhibiting the enzymes in mitochondria that make ATP. Intravenous injection of an unnaturally high concentration of potassium chloride, such as in the execution of prisoners in parts of the United States, quickly stops the heart by eliminating the cell potential necessary for muscle contraction.

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).

Many substances regarded as poisons are toxic only indirectly, by toxication. An example is "wood alcohol" or methanol, which is not poisonous itself, but is chemically converted to toxic formaldehyde and formic acid in the liver. Many drug molecules are made toxic in the liver, and the genetic variability of certain liver enzymes makes the toxicity of many compounds differ between individuals.

Exposure to radioactive substances can produce radiation poisoning, an unrelated phenomenon.

In animals and humans chronic intake of silver products commonly leads to gradual accumulation of silver compounds in various parts of the body. As in photography (where silver is useful because of its sensitivity to light), exposure of pale or colourless silver compounds to sunlight decomposes them to silver metal or silver sulfides. Commonly these products deposit as microscopic particles in the skin, in effect a dark pigment. This condition is known as argyria or argyrosis.

Chronic intake also may lead to silver pigments depositing in other organs exposed to light, particularly the eyes. In the conjunctiva this is not generally harmful, but it also may affect the lens, leading to serious effects.

Localised argyria often results from topical use of substances containing silver, such as some kinds of eye drops. Generalized argyria results from chronically swallowing or inhaling silver compounds, either for home medicines purposes, or as a result of working with silver or silver compounds.

While silver is potentially toxic to humans at high doses, the risk of serious harm from low doses, given over a short term, is slight. Treatment of external infections is considered safe; oral use of colloidal silver is safe for short term administration if the dose is low. Silver is used in some medical appliances because of its anti-microbial nature, which stems from the oligodynamic effect. Chronic ingestion or inhalation of silver preparations (especially colloidal silver) can lead to argyria in the skin and other organs. This is not life-threatening, but is considered by most to be cosmetically undesirable.

The reference dose, published by the United States Environmental Protection Agency in 1991, which represents the estimated daily exposure that is unlikely to incur an appreciable risk of deleterious effects during a lifetime, is 5 µg/(kg·d).

Argyria worsens and builds up as exposure to silver continues, and does not resolve once exposure stops.

Cutaneous radiation syndrome (CRS) refers to the skin symptoms of radiation exposure. Within a few hours after irradiation, a transient and inconsistent redness (associated with itching) can occur. Then, a latent phase may occur and last from a few days up to several weeks, when intense reddening, blistering, and ulceration of the irradiated site are visible. In most cases, healing occurs by regenerative means; however, very large skin doses can cause permanent hair loss, damaged sebaceous and sweat glands, atrophy, fibrosis (mostly Keloids), decreased or increased skin pigmentation, and ulceration or necrosis of the exposed tissue. Notably, as seen at Chernobyl, when skin is irradiated with high energy beta particles, moist desquamation (peeling of skin) and similar early effects can heal, only to be followed by the collapse of the dermal vascular system after two months, resulting in the loss of the full thickness of the exposed skin. This effect had been demonstrated previously with pig skin using high energy beta sources at the Churchill Hospital Research Institute, in Oxford.

There are no specific symptoms associated with claims of EHS and reported symptoms range widely between individuals. They include headache, fatigue, stress, sleep disturbances, skin prickling, burning sensations and rashes, pain and ache in muscles and many other health problems. In severe cases such symptoms can be a real and sometimes disabling problem for the affected person, causing psychological distress. There is no scientific basis to link such symptoms to electromagnetic field exposure.

The prevalence of some reported symptoms is geographically or culturally dependent and does not imply "a causal relationship between symptoms and attributed exposure". Many such reported symptoms overlap with other syndromes known as symptom-based conditions, functional somatic syndromes, and IEI (idiopathic environmental intolerance).

Those reporting electromagnetic hypersensitivity will usually describe different levels of susceptibility to electric fields, magnetic fields, and various frequencies of electromagnetic waves. Devices implicated include fluorescent and low-energy lights, mobile, cordless/portable phones, and WiFi. A 2001 survey found that people self-diagnosing as EHS related their symptoms most frequently to mobile phone base stations (74%), followed by mobile phones (36%), cordless phones (29%), and power lines (27%). Surveys of electromagnetic hypersensitivity sufferers have not been able to find any consistent pattern to these symptoms.

Cadmium is a naturally occurring toxic heavy metal with common exposure in industrial workplaces, plant soils, and from smoking. Due to its low permissible exposure to humans, overexposure may occur even in situations where trace quantities of cadmium are found. Cadmium is used extensively in electroplating, although the nature of the operation does not generally lead to overexposure. Cadmium is also found in some industrial paints and may represent a hazard when sprayed. Operations involving removal of cadmium paints by scraping or blasting may pose a significant hazard. Cadmium is also present in the manufacturing of some types of batteries. Exposures to cadmium are addressed in specific standards for the general industry, shipyard employment, construction industry, and the agricultural industry.

Lead poisoning can cause a variety of symptoms and signs which vary depending on the individual and the duration of lead exposure. Symptoms are nonspecific and may be subtle, and someone with elevated lead levels may have no symptoms. Symptoms usually develop over weeks to months as lead builds up in the body during a chronic exposure, but acute symptoms from brief, intense exposures also occur.

Symptoms from exposure to organic lead, which is probably more toxic than inorganic lead due to its lipid solubility, occur rapidly. Poisoning by organic lead compounds has symptoms predominantly in the central nervous system, such as insomnia, delirium, cognitive deficits, tremor, hallucinations, and convulsions.

Symptoms may be different in adults and children; the main symptoms in adults are headache, abdominal pain, memory loss, kidney failure, male reproductive problems, and weakness, pain, or tingling in the extremities.

Early symptoms of lead poisoning in adults are commonly nonspecific and include depression, loss of appetite, intermittent abdominal pain, nausea, diarrhea, constipation, and muscle pain. Other early signs in adults include malaise, fatigue, decreased libido, and problems with sleep. An unusual taste in the mouth and personality changes are also early signs.

In adults, symptoms can occur at levels above 40 μg/dL, but are more likely to occur only above 50–60 μg/dL. Symptoms begin to appear in children generally at around 60 μg/dL. However, the lead levels at which symptoms appear vary widely depending on unknown characteristics of each individual. At blood lead levels between 25 and 60 μg/dL, neuropsychiatric effects such as delayed reaction times, irritability, and difficulty concentrating, as well as slowed motor nerve conduction and headache can occur. Anemia may appear at blood lead levels higher than 50 μg/dL. In adults, abdominal colic, involving paroxysms of pain, may appear at blood lead levels greater than 80 μg/dL. Signs that occur in adults at blood lead levels exceeding 100 μg/dL include wrist drop and foot drop, and signs of encephalopathy (a condition characterized by brain swelling), such as those that accompany increased pressure within the skull, delirium, coma, seizures, and headache. In children, signs of encephalopathy such as bizarre behavior, discoordination, and apathy occur at lead levels exceeding 70 μg/dL. For both adults and children, it is rare to be asymptomatic if blood lead levels exceed 100 μg/dL.

Coal ash, also known as coal combustion residuals (CCRs), is the particulate residue that remains from burning coal. Depending on the chemical composition of the coal burned, this residue may contain toxic substances and pose a health risk to workers in coal-fired power plants.

Symptoms arise 4–12 hours after exposure to an organic dust, and generally last from one to five days. Common generalised symptoms include fever over 38 °C, chills, myalgia and malaise. The most frequent respiratory symptoms are dyspnea and a dry cough, while a wheeze may be present less commonly. Headache, rhinitis, conjunctivitis and keratitis can also be present, and skin irritation may occur in those handling grain.

Respiratory function may worsen to the point where hypoxia occurs, and damage to the airways may lead to non-cardiogenic pulmonary edema one to three days post exposure.

Laboratory investigations may show a raised white cell (and specifically neutrophil) count, while a chest X-ray is often normal or shows minimal interstitial infiltration.

The use of podiatry drills, in the absence of engineering controls and personal protective equipment, is an occupational hazard to the healthcare provider. Nail dust collected during foot care procedures performed in office settings has been found to contain keratin, keratin hydrolysates, microbial debris, and viable fungal elements, including dermatophytes (most commonly "Trichophyton rubrum") and saprotrophs. Exposure to nail dust and the associated risk will vary with the policies and practices in place, the type of podiatry drill used, therapy technique, frequency of procedures, personal protective equipment utilized and the use of ventilation systems.

Chronic poisoning usually presents with symptoms affecting multiple systems, but is associated with three main types of symptoms: gastrointestinal, neuromuscular, and neurological. Central nervous system and neuromuscular symptoms usually result from intense exposure, while gastrointestinal symptoms usually result from exposure over longer periods. Signs of chronic exposure include loss of short-term memory or concentration, depression, nausea, abdominal pain, loss of coordination, and numbness and tingling in the extremities. Fatigue, problems with sleep, headaches, stupor, slurred speech, and anemia are also found in chronic lead poisoning. A "lead hue" of the skin with pallor and/or lividity is another feature. A blue line along the gum with bluish black edging to the teeth, known as a Burton line, is another indication of chronic lead poisoning. Children with chronic poisoning may refuse to play or may have hyperkinetic or aggressive behavior disorders. Visual disturbance may present with gradually progressing blurred vision as a result of central scotoma, caused by toxic optic neuritis.