OHS knows all about Hg (mercury).
(Link no longer valid) http://www.ccohs.ca/oshanswers/chemicals/chem_profiles/mercury/health_mercury.html
The text of the web page on March 3, 2011 is:
Document last updated on December 21, 1998
Health Effects of Mercury
- What are the main health hazards associated with breathing in Mercury?
- What happens when Mercury comes into contact with my skin?
- Can Mercury hurt my eyes?
- What happens if Mercury is accidentally swallowed (enters the digestive system)?
- What are the long term health effects of exposure to Mercury?
- Will Mercury cause cancer?
- Will Mercury cause any problems with my reproductive system?
- Will Mercury cause effects on the fetus/unborn baby?
- Will Mercury act in a synergistic manner with other materials (will its effects be more than the sum of the effects from the exposure to each chemical alone)?
- Is there potential for Mercury to build-up or accumulate in my body?
What are the main health hazards associated with breathing in Mercury?
Harmful effects due to short-term exposure to elemental mercury are rarely seen any more because of strict controls used in workplaces where mercury exposure might occur. Historically, short-term exposure to high concentrations of mercury vapour caused harmful effects on the nervous, digestive and respiratory systems, and the kidneys. In most cases, exposure occurred when mercury was heated.
Initial exposure to high concentrations of mercury vapour produces symptoms similar to “metal fume fever” including fatigue, fever, and chills. Respiratory system effects include cough, shortness of breath, tightness and burning pains in the chest and inflammation of the lungs. Occupational exposure to 1 to 44 mg/m3 of mercury vapour for 4 to 8 hours caused chest pain, cough, coughing up blood, impaired lung function and inflammation of the lungs. In some cases, a potentially life-threatening accumulation of fluid in the lungs (pulmonary edema) has occurred. Exposure to high, but unspecified, concentrations of mercury vapour has caused death due to respiratory failure. All of the reported deaths resulted from inhaling mercury vapours formed upon heating mercury.
Several case reports have described harmful nervous system effects following inhalation of high concentrations of mercury vapour. The most prominent symptoms include tremors (initially affecting the hands and sometimes spreading to other parts of the body), emotional instability (including irritability, excessive shyness, a loss of confidence and nervousness), sleeplessness, memory loss, muscle weakness, headaches, slow reflexes and a loss of feeling or numbness.
A classic sign of exposure to high concentrations of mercury is inflammation of inside of the mouth (stomatitis), sometimes with a metallic taste, excessive salivation and difficulty swallowing. Other digestive system effects include abdominal pains, nausea, vomiting and diarrhea.
Kidney injury is common following exposure to high concentrations of mercury. Reported effects range from increased protein in the urine to kidney failure. Exposure to high concentrations of mercury has also caused increased blood pressure and heart rate.
What happens when Mercury comes into contact with my skin?
Elemental mercury is not known to directly irritate the skin. However, an allergic skin reaction may develop following contact with mercury. For further information, refer to “What are the long term health effects of exposure to Mercury?” below. Elemental mercury liquid and vapour can be absorbed through the skin and may contribute to the overall absorption and toxicity.
Can Mercury hurt my eyes?
There is very little relevant information about the effects of getting liquid mercury in the eyes. It is probably not a direct eye irritant. In one case, droplets of mercury accumulated under the surface of the cornea in an person forcefully sprayed with mercury liquid. After two days, the cornea cleared and vision was normal. High concentrations of mercury vapour can cause redness, burning and inflammation of the eyes.
What happens if Mercury is accidentally swallowed (enters the digestive system)?
Elemental mercury is poorly absorbed from the gastrointestinal tract and is more toxic following inhalation. In one report, ingestion of 204 gm did not cause harmful effects. In a second report, ingestion of 220 mL (approximately 3.0 kg) caused immediate effects such as tremor, irritability, forgetfulness and fatigue. It is uncertain whether liver effects observed several months later were related to the mercury exposure. Ingestion is not a typical route of occupational exposure. Although airborne droplets of elemental mercury are actually more likely to enter the gastrointestinal system rather than the lungs, resulting in lower absorption.
What are the long term health effects of exposure to Mercury?
The harmful effects of long-term exposure to elemental mercury are generally thought to be caused by inhalation exposure. However, mercury liquid and vapour are absorbed through the skin in small amounts and this route of exposure can contribute to the overall exposure. Effects following absorption through the skin are expected to be similar to those reported for long-term inhalation exposure.
Mercury levels in urine are often used as a general indicator of how much exposure to mercury has occurred. As a result, urine mercury levels rather than airborne levels are provided in some of the reports which compare mercury exposures to specific health effects. Urine mercury levels are reported in micrograms/gram of creatinine (a component of the urine). The relationship between airborne mercury levels and urine mercury levels is complicated and depends on many factors, including other sources of mercury exposure and between individual differences. Several studies indicate that an airborne exposure of 0.025 mg/m3 mercury compares to approximately 37 micrograms of mercury/gram of creatinine in the urine. Urine mercury levels in adults without occupational exposure are typically less than 3 micrograms/gram of creatinine. Sources of non-occupational exposure to inorganic mercury include new dental fillings.
In this review, urinary mercury levels below 35 micrograms/gram of creatinine are considered to reflect relatively low mercury exposure; 35 to 50 micrograms/gram of creatinine reflects moderate exposure; 50 to 100 micrograms/gram of creatinine reflects moderately high exposure and above 100 micrograms/gram of creatinine reflects high exposure.
EFFECTS ON THE NERVOUS SYSTEM:
Effects on muscle coordination, mood, behaviour, memory, feeling and nerve conduction have been reported following long-term occupational exposure to mercury. These effects are often observed in employees with moderately high or high exposure to mercury. At lower exposures, the results are inconclusive with no effects being reported in some studies and mild effects reported in other studies. Although improvement has been observed upon removal of the person from the source of exposure, it is possible that some of the changes may be irreversible. The nervous system effects of mercury toxicity are sometimes referred to as “Mad Hatter’s Disease” since mercurous nitrate was used in making felt hats.
A classic sign of mercury toxicity is a fine tremor, usually of the fingers, hands or arms and occasionally the eyelids, lips, tongue, and whole body. Many occupational studies indicate that tremors become more pronounced with longer exposures to mercury. Tremors are thought to be a sensitive indicator for long-term low-level exposure to mercury vapour. One report described tremors in employees with average exposures as low as 0.026 mg/m3 for an average of 15 years.
Behaviour and personality changes such as irritability, excitation and shyness, psychotic reactions such as delirium and hallucinations, loss of appetite, tiredness, sleeplessness, short-term memory loss and impaired nerve conduction have also been reported following long-term exposure. In one study, subtle behaviourial effects were detected in dentists with moderate mercury exposure.
Damage to the nerves of the arms and legs (polyneuropathy) has been reported in employees with high exposures. Reduced sensation and strength in the arms and legs, muscle cramps and decreased nerve conduction have been observed. Employees with episodes of very high exposure appear to be more at risk of developing these effects. Studies of employees in a chlor-alkali plant showed mild polyneuropathy in employees exposed to high levels of mercury. Signs included abnormalities in nerve conduction tests with reduced sensation and increased tremor of the arm.
EFFECTS ON THE KIDNEY:
Many occupational studies indicate that moderate to high exposure to mercury can cause harmful effects on the kidneys. When urine mercury levels are low to moderate, the results are inconclusive with no effects being reported in some studies and mild effects reported in others.
Early indicators of kidney injury include increased levels of protein in the urine (proteinuria) and increased levels of certain enzymes in the blood and urine. Proteinuria is commonly observed in studies reporting kidney effects. Less often, changes to the structure of the kidneys have been shown. An increase in deaths from kidney disease in people occupationally exposed to mercury was not observed in one study.
SKIN SENSITIZATION:
Allergic skin sensitization has been reported in people with occupational exposure to mercury liquid or vapour. Once a person is sensitized to a chemical, contact with even a small amount causes outbreaks of dermatitis with symptoms such as skin redness, itching, rash and swelling. This can spread from the hands or arms to other parts of the body. Occupational skin sensitization to mercury has been observed in people exposed to mercury in dental amalgams, tattoos or breakage of medical instruments. Positive patch tests were obtained in a dentist, five doctors, a nurse’s aid, a mercury recycling employee and a pipeline repairman who had developed of red, dry, itchy skin (contact dermatitis) following occupational exposure. Previous history of allergies was not discussed for any of these cases. Skin sensitization to mercury has also been reported in the general public.
EFFECTS ON THE DIGESTIVE SYSTEM:
Limited information suggests that long-term exposure to mercury vapour can cause inflammation and ulceration of the inside of the mouth, sore gums, drooling, diarrhea and other effects on the digestive system. No exposure information is reported, but presumably the concentrations were high.
EFFECTS ON THE HEART:
Mercury may affect the heart producing increased blood pressure and/or heart rate. Two studies of employees with long-term exposure to low levels of mercury showed no effects on blood pressure or heart rhythm, as measured by electrocardiogram (ECG). A few other studies have shown effects on the heart including increased blood pressure and heart rate and abnormal ECG results. More deaths due to cardiovascular problems were observed in employees exposed to mercury in the chlor-alkali industry. These studies are limited by factors such as exposure to other potentially harmful chemicals at the same time and weak exposure information.
EFFECTS ON THE IMMUNE AND ENDOCRINE SYSTEMS:
In most studies, effects on the immune and endocrine systems were not observed in employees exposed to mercury. However, altered immune response has been suggested in a few studies.
EFFECTS ON THE RESPIRATORY SYSTEM:
Very little information is available regarding effects on the respiratory system from long-term exposure. Two studies reported persistent cough in employees exposed to mercury vapour for several weeks. Another study reported no respiratory symptoms, X-ray abnormalities or impaired pulmonary function in employees exposed to mercury vapour levels up to 0.27 mg/m3 for more than 6 years.
EFFECTS ON THE EYE:
Long-term occupational exposure to mercury has caused a grayish-brown or yellow discoloration in the eyes of some people. This haze is not thought to affect vision. A gray band through the cornea (band keratopathy) has also been reported in a few people. In one study, poor colour vision was observed in 33 employees with moderately high to high urine mercury levels.
Will Mercury cause cancer?
The International Agency for Research on Cancer (IARC) has determined that there is inadequate evidence in humans and animals for the carcinogenicity of mercury and mercury compounds. The overall IARC evaluation for metallic mercury and inorganic mercury compounds is that they are not classifiable as to their carcinogenicity to humans (Group 3).
In most studies, increased cancer rates were not observed in people with occupational exposure. Brain tumours were increased in dentists and dental nurses exposed to metallic mercury, but this outcome was not observed in other similar populations. In another study, prostate and lung cancers were associated with exposure to metallic mercury. Other studies could not be interpreted because of study design limitations such as multiple chemical exposures.
Will Mercury cause any problems with my reproductive system?
Although it is not possible to draw firm conclusions based on the limited human information available, exposure to mercury may reduce fertility in females. Effects on male fertility have generally not been observed. There is no relevant animal information available.
In one study, fertility was decreased in female dental assistants who prepared 30 or more dental fillings per week and had poor work hygiene practices. There was also some evidence of decreased fertility in a group of employees exposed to mercury at a lamp factory. Both of these studies had design limitations. Complications during pregnancy and delivery and increased menstrual disorders have also been seen in some studies. However, all of the studies had design limitations including inadequate exposure assessment, inadequate controls and incomplete reporting of the data.
Effects on fertility were not seen in three studies of men occupationally exposed to mercury. One study showed that the wives of men occupationally exposed to moderately high concentrations of mercury had more miscarriages, but another study did not show this effect. Two studies showed no harmful effects on pregnancy when the father was exposed to mercury.
Will Mercury cause effects on the fetus/unborn baby?
While it is not possible to draw firm conclusions based on the limited human information available, exposure to mercury has generally not caused harmful effects in the unborn child or more miscarriages. Two animal studies do indicate that mercury exposure during pregnancy can cause subtle behavioral changes in offspring, in the absence of harmful effects in the mothers. Several human population studies have investigated pregnancy outcome in women routinely exposed to low levels of mercury in the workplace. Two large studies of dental assistants and dentists did not report an increase in birth defects. Two smaller studies, both with study design limitations, reported birth defects (such as spina bifida and dislocation of the hip). One incompletely reported study suggested decreased birth weights.
A small number of case reports have not described harmful effects on the unborn child following brief exposure of the mother to high levels of mercury during pregnancy. Another case report describes a normal pregnancy outcome in a woman occupationally exposed to low levels of mercury vapour throughout pregnancy. No conclusions can be drawn from one other case report where the infant was also deprived of oxygen during delivery.
Most human population studies have not shown more miscarriages in women occupationally exposed to mercury. A few studies with significant design limitations have shown more miscarriages.
Will Mercury act in a synergistic manner with other materials (will its effects be more than the sum of the effects from the exposure to each chemical alone)?
In one animal study, the offspring of pregnant rats exposed to both methylmercury and elemental mercury had more pronounced behaviourial effects than rats exposed to elemental mercury alone. Similar effects were not observed in the offspring of rats exposed to methylmercury alone. No conclusions can be drawn from one study which indicated that the mutagenic effects of elemental mercury are enhanced by smoking. This study was incompletely reported.
Exposure to other metals at the same time, the use of penicillin-type antibiotics, and ingestion of ethanol in alcoholic beverages can the influence excretion of elemental mercury.
Is there potential for Mercury to build-up or accumulate in my body?
Elemental mercury is a heavy liquid. The vapour evaporates from the liquid and evaporation occurs more rapidly when the liquid is heated. The vapour is well absorbed following inhalation. It accumulates in the kidney and the brain. Elemental mercury is excreted from the body slowly. It has an elimination half-life of 40-60 days. Most elemental mercury is excreted in exhaled air, and small amounts in the feces and urine. Very small amounts can be eliminated in sweat, saliva and milk. Following ingestion, elemental mercury is poorly absorbed and most of it is excreted in the feces. Elemental mercury liquid and vapour can be absorbed through the skin in small amounts. Elemental mercury is transferred to the developing child in a pregnant women.