|Mercury Testing - Air Sampling: IAQ Tech Tip #39 Aerotech Labs Mercury effects and how to determine exposure through mercury test kits|
|Mercury is most commonly known as the silver liquid that is seen in thermometers. Unknown to many is the fact that mercury is also a widely used substance in industrial production. Along with this use has come the possibility of contamination of the environment. Although, the EPA has for some time banned the use of mercury in latex paints, exterior paints (was formerly used as a fungicide), and in pesticides, mercury can still be found in batteries, and in chlorine- alkali production. Mercury can also be found in older gas meter regulators, and blood pressure gauges. Some experts claim that there is little harm in small amounts, but there can be a great concern when the liquid vaporizes.|
Mercury, an odorless substance, tends to easily vaporize when it comes in contact with a surface and is easily tracked around or released into the air by such acts as vacuuming and being walked upon. Humans can come in contact with mercury through occupational, environmental, or accidental exposure. An estimated 80% of mercury is eventually released back into the environment. Because it is easily vaporized, air around chlorine-alkali plants, smelters, municipal incinerators, sewage treatment plants and even contaminated soils may contain increased levels of mercury.
Recent News Coverage: Mercury has been a hot topic among the media lately. A recent edition of the television show 60 Minutes highlighted concerns about mercury exposure in patients receiving silver dental fillings with mercury-containing amalgam. Another press release from the utility, Nicor Gas, recently explained the reasons why they have decided to test for mercury in about 200,000 homes in the Chicago area. Their tests came about when they found mercury in a home that had recently had old pressure regulators removed from it. If you would like to read the Nicor statement visit: http://www.nicorinc.com/gas/wnew/8_30_00b.html
Health Effects: Exposure to mercury can occur through inhalation, ingestion or dermal absorption. The amount of mercury absorbed by the body, and thus the degree of toxicity, is dependent upon the chemical form of mercury. For instance, ingested elemental mercury is only 0.01% absorbed, but methyl mercury is nearly 100% absorbed from the gastrointestinal tract. The biological half-life of mercury is 60 days. Thus, even though exposure is reduced, the body burden will remain for at least a few months. Elemental mercury is most hazardous when inhaled. Only about 25% of an inhaled dose is exhaled.
In the human body, mercury accumulates in the liver, kidney, brain, and blood. Mercury may cause acute or chronic health effects. Acute exposure (i.e., short term, high dose) is not as common today due to greater precautions and decreased handling. However, severe acute effects may include severe gastrointestinal damage, cardiovascular collapse, or kidney failure, all of which could be fatal. Inhalation of 1-3 mg/m3 for 2-5 hours may cause headaches, salivation, a metallic taste in the mouth, chills, cough, fever, tremors, abdominal cramps, diarrhea, nausea, vomiting, tightness in the chest, difficulty breathing, fatigue, or lung irritation. Symptoms may be delayed in onset for a number of hours. Chronic effects include central nervous system effects, kidney damage and birth defects. Genetic damage is also suspected.
Mercury can affect the nervous system as well. These are the most critical effects of chronic mercury exposure from adult exposure as they are consistent and pronounced. Some elemental mercury is dissolved in the blood and may be transported across the blood/brain barrier, oxidized and retained in brain tissue. Elimination from the brain is slow, resulting in nerve tissue accumulation. Symptoms of chronic mercury exposure on the nervous system include: increased excitability, mental instability, tendency to weep, fine tremors of the hands and feet, and personality changes. The term "Mad as a Hatter" came from these symptoms, which were a result of mercury exposure in workers manufacturing felt hats using a mercury-containing process. Kidney damage can occur and includes increased protein in the urine and may result in kidney failure at high dose exposure.
Women can also be exposed to birth defects including neurological damage from methyl mercury. The manifestations of mild exposure include delayed developmental milestones, altered muscle tone and tendon reflexes, and depressed intelligence. Mercury exposure in children can cause a severe form of poisoning termed acrodynia. Acrodynia is evidenced by pain in the extremities, pinkness and peeling of the hands, feet and nose, irritability, sweating, rapid heartbeat and loss of mobility.
Sampling for Mercury: Sampling for mercury should be done carefully. Since mercury can be readily absorbed through inhalation or skin contact, you must wear the proper equipment to avoid exposure. Sampling can be done through two methods: air and surface.
Air samples can be taken utilizing a solid sorbent tube. Each personal sampling pump should be calibrated with a representative sampler inline. Break the ends of the sampler immediately prior to sampling and attach the sampler to the pump with flexible tubing. Then sample at an accurate flow rate of 0.15 to 0.25 L/min for a sample size of between 2 and 100 L. Cap the sampler and pack securely for shipment to the laboratory. Alternatively there are also surface sampling methods available that can be taken by wiping surface areas for possible mercury contamination.