Listed metals in specified products
The State of Minnesota is committed to reducing the volume of waste generated in our communities. However, the toxicity of wastes also must be reduced to protect and preserve the environment. Ways to achieve this goal include looking at how products are made, working to reduce toxic substances introduced through the manufacturing process, and keeping these substances out of the waste stream whenever it is possible or practical.
In 1991, the Minnesota Legislature passed laws requiring reduction of four metals in specified products (Minn. Stat. 115A.9651). These metals -- lead, mercury, hexavalent chromium, and cadmium -- all have known adverse effects on public health and the environment. They are called "listed" metals because they are defined as toxic in a list contained in the Resource Conservation and Recovery Act (RCRA), the federal law governing hazardous waste management. The law applies to an estimated 1,000 products made or sold in Minnesota, including inks, dyes, paints, pigments and one fungicide.
(Minnesota also has a Selected Toxics in Packaging statute, which is related to the Toxics in Specified Products law.)
For some products containing listed metals, there are no safe substitutes. For others, substitutes may be available, but are impractical or costly for manufacturers. However, many businesses, both within Minnesota and nationwide, are making serious efforts to develop successful products that do not use listed metals. This "product stewardship" -- the attempt to develop or use products that do not adversely affect the environment and are sustainable over the long term -- is one important way to stop pollution at its source.
While the health and/or environmental impacts of many hazardous substances are not completely understood, substantial research and information is available about the four listed metals covered by Minnesota's toxics in specified products law. The following information, taken from the U.S. Department of Health and Human Services Toxicological Reports, illustrates why individuals, businesses and regulators want to reduce the presence of listed metals in the state's waste.
In addition to what is known about listed metals, there is also growing research that suggests that listed metals may be "endocrine disrupters" or "hormone mimics." Certain substances mimic or disrupt natural processes in the bodies of humans and animals that govern normal development of the nervous system, immune system and reproductive system. These endocrine disrupters have been implicated in research involving both people and animals.
Lead
Lead is a naturally occurring metal found in the earth's crust. However, most of the lead dispersed throughout the environment comes from human activity. Leaded gasoline was one of the major sources of airborne lead. Other sources of lead released to the air include burning fuel, such as coal and oil, industrial processes and burning solid waste. The largest use of lead is in the production of some types of batteries. It is also used in ammunition, ceramic glazes, and medical, scientific and military equipment.
The release of lead to the air is now less than the release of lead to the soil. Most of the elevated levels of lead in soils comes from landfills, leaded paint, mining wastes, ammunition manufacturing, and other industrial activities such as battery production. Lead is removed from the air by rain and, once deposited on soil, usually adheres to soil particles.
The levels of lead may build up in plants and animals in areas where air, water, or soil are contaminated with lead. If animals eat contaminated plants or animals, most of the lead that they eat will pass though their bodies. It is the small amount absorbed that can cause harmful effects.
For the general population, most exposure results from eating foods containing lead or from leaded paint. Lead can be found in a variety of foods including produce, meats, grains, seafood, soft drinks and wine. Usually, low levels of lead are found in drinking water. However, the amount of lead in drinking water can increase if the water supply is acidic, leaching lead from lead pipes, solder or brass faucets.
Large numbers of workers are potentially exposed to lead in the workplace. People employed in lead smelting and refining jobs, rubber products and plastic industries, steel welding or cutting operations, battery manufacturing plants, construction work, those who work at municipal waste incinerators, pottery and ceramics industries or remove old lead-based paint may all be exposed. The Occupational Safety and Health Administration (OSHA) requires that a worker with a blood-lead level over 40 ug/deciliter be removed from the area of exposure. A study of workers in a ceramics industry indicated that family members of exposed workers also had elevated blood-lead levels, most likely because of the dust accidentally brought home by workers.
Inhalation is the main pathway of exposure for people whose occupation exposes them to lead particles. Once in the lower respiratory tract, lead is almost completely absorbed. Absorption of lead in adults through ingestion is relatively low, unless ingested while the person is fasting. However, the rate of absorption through ingestion for young children is four to five times higher than for adults. Exposure data is expressed in terms of absorbed dose, usually measured as levels of lead in the blood.
Estimates of blood-lead levels for children under five years old indicated that nearly nine percent, or approximately two million children have blood-lead levels of 10 ug/deciliter or higher, which the Center for Disease Control considers to be the level indicating lead poisoning.
There is no beneficial purpose for lead in the human body. Lead has been shown to affect virtually every major organ in the body. The most sensitive organs appear to be the nervous system (particularly in children), the circulatory system and the cardiovascular system. In addition, colic is a consistent early symptom of lead poisoning. In adults, symptoms of neurological effects include dullness, irritability, poor attention span, headaches, muscular tremors, loss of memory, and hallucinations. The condition may then worsen, sometimes abruptly, to delirium, convulsions, paralysis, coma and death.
In children, many of the same symptoms occur along with hyperirritability and convulsions. There is a greater incidence of permanent neurological and cognitive impairments in children. Even at lower levels without the severe symptoms described above, there may be permanent damage.
A large body of literature clearly indicates that high levels of lead cause adverse effects on both male and female human reproductive functions. Lead is a teratogen that can cause fetal malformation, a mutagen that can affect both sperm and eggs, and a reproductive toxin that can impair fertility. Women who are exposed during pregnancy have experienced miscarriages and stillbirths. Several studies in males indicates that at moderate blood-lead levels (40-50 micrograms (ug)/deciliter) sperm production may be affected. Other studies, while of limited sample size or lacking a matched control group, provide evidence for lead-induced endocrine disturbances and reproductive disjunction in male workers exposed to lead.
Mercury
Most people have seen mercury in such commonly used items as thermometers, sphygmomanometers used to detect blood pressure, and switches in thermostats and vehicles and in certain pigments. It is an element (abbreviated Hg by chemists), one of the basic building blocks of life, and occurs naturally in several forms.
Studies show that 75 percent of the airborne mercury deposited in the environmental is from human, not natural, sources. As a metal, mercury persists in the environment. It is difficult to destroy by burning or bacterial breakdown and in bioaccumulates in the body. Mercury can easily exist as a vapor, so it can be inhaled and absorbed into the blood. It affects a variety of internal organs and methylmercury, an organic form of mercury, affects the central nervous system.
Cadmium
Cadmium is an element (Cd) that occurs naturally in the earth's crust, but most cadmium found in the environment is the result of human activities. Most cadmium used worldwide is a byproduct of refining other metals, such as zinc, lead or copper. Cadmium is used mainly in batteries, pigments, metal coatings and plastic.
Cadmium does not break down in the environment, but it can change forms, some of which dissolve in water. Dissolved cadmium can bioaccumulate up the food chain. The U.S. Environmental Protection Agency (USEPA)had classified cadmium as a probable human carcinogen.
The two main routes of exposure for the general population are by inhalation of cadmium particles and ingestion of food or water containing cadmium. Most cadmium in the environment is in the form of particulate matter in the air and is generated from human activities such as mining, smelting, fuel combustion and incineration of waste or sewage sludge. Cigarette smokers inhale cadmium in the smoke.
Dissolved cadmium can bioaccumulate up the food chain, so ingestion is a common route of exposure. The accumulation of cadmium has been reported in food crops, livestock, wildlife and aquatic organisms. Cadmium entering the body is excreted slowly over time, but too much cadmium can overload the kidneys and cause damage. Cadmium is a cumulative toxin, so long-term exposure at an elevated level is a concern.
Workers exposed to cadmium through inhalation have shown signs of renal damage. At higher levels of exposure, calcium deficiencies and bone disorders have been reported, but effects on bones generally appear only after the kidneys have been damaged. Limited evidence exists for an association between inhalation exposure to cadmium and reproductive effects. Female rats exposed to cadmium four to five months prior to mating and during gestation, showed damage to the offspring. The effects were noted at the lowest concentration tested (0.02 mg/m3). These studies indicate that cadmium is a developmental toxin in animals.
The EPA has classified cadmium as a probable human carcinogen by inhalation based on animal and human data. The kidneys are the organs most affected after long-term oral exposure. At higher levels, cadmium decreases gastrointestinal uptake of iron, which can result in anemia if a person's diet is low in iron. Painful bone disorders have been observed in some people chronically exposed to food with elevated levels of cadmium. Neurological effects such as lower verbal IQ and disruptive behavior have been reported, but these studies are not definitive because the level of cadmium exposure was unknown and could not be separated from the effects of lead exposure.
Although the evidence for neurotoxicity is uncertain in human studies, it is fairly strong from animal studies, showing decreased motor activities, weakness, and muscle atrophy. Studies of rats and mice indicate that fetal toxicity may be a concern for females orally exposed to cadmium prior to, and during pregnancy. In addition, reproductive success decreases for both male and female rats orally exposed to cadmium.
Hexavalent Chromium
Chromium is a natural element found in rocks, animals, plants, and soil. Chromium can take several different chemical forms or valent states; chromium, trivalent chromium or hexavalent chromium. Trivalent chromium occurs naturally, and in small amounts is an essential nutrient for humans. Hexavalent chromium and chromium are generally produced by industry. Hexavalent chromium rarely occurs in nature. It is very toxic and is used in chrome plating, in manufacturing dyes and pigments, leather tanning and wood preserving.
Individuals who work in industries that process or use chromium compounds can be exposed to higher than normal levels of chromium. An estimated 305,000 workers in the United States are exposed occupationally. Those industries include stainless steel welding, chromate production, chrome platers, chrome pigment manufactures, painters, battery makers, printers, candle makers, and cement makers.
People who live near industrial facilities that use or manufacture hexavalent chromium, cement plants, or landfills with wastes that contain chromium may also be exposed to higher levels of chromium than the general population. Busy roadways that generate vehicle exhaust and cement particles may also increase exposure for near-by residents. Tobacco products also contain chromium.
There are three routes of exposure for hexavalent chromium, inhalation of airborne particles, ingestion, and to a much lesser extent, through the skin. For the general population, the most common route of exposure is by eating foods containing hexavalent chromium. Only very small amounts of hexavalent chromium can enter the body through the skin unless the skin is damaged.
Occupations that lead to exposure by inhalation to hexavalent chromium, such as chromate and chromate pigment production and chrome plating, are associated with respiratory disease and lung cancer. Nasal septum perforation and other respiratory effects have been reported among workers chronically exposed to hexavalent chromium compounds.
The Department of Health and Human Services and the International Agency for Research on Cancer has determined that the following hexavalent chromium compounds are carcinogenic in humans: calcium chromate, zinc chromate, strontium chromate, lead chromate as well as those compounds used in chromate production, chromate pigment production and chromium plating.
Oral exposure indicates that hexavalent chromium has the most impact on human blood-cell profiles and the gastrointestinal system. Nausea and vomiting were reported when hexavalent chromium dust was ingested. Oral ulcers, diarrhea, abdominal pain, indigestion, and vomiting resulted from drinking badly contaminated well water. However, no evidence of cancer has been found in mice following long-term exposure to hexavalent chromium in drinking water. Reproductive effects have not been reported in humans, but oral exposure to hexavalent chromium caused severe reproductive and developmental effects in mice.
Landfills
More than half of the solid waste, including demolition, construction and industrial waste, generated in Minnesota is landfilled. One of the byproducts of landfilling is leachate. Leachate is produced as water from rain or melted snow percolates through the waste. It contains particles, metals and chemicals that are picked up from the waste. All municipal solid waste (MSW) and most industrial landfills have liners, which contain the leachate, and collection systems, which collect and pump the leachate out of the landfill.
In some communities, the leachate is trucked to the local wastewater treatment facility for treatment and eventual discharge. The sludge from wastewater treatment facilities is spread on nearby fields. Some landfills must pay a strength charge to the wastewater treatment plants, meaning that the more contaminated the leachate, the greater the cost of treatment. The strength of the leachate can be a problem for smaller treatment facilities that have to incorporate the leachate slowly in order not to overwhelm the system. In essence, the leachate is diluted by the other wastewater prior to treatment. Landfill gas is generated as materials decompose. The constituents of the waste determine the composition of the gas. Because it volatilizes into the air at low temperatures, mercury has been detected in landfill gas.
In some communities, trucking large volumes of leachate may not be practical or the distance to the nearest treatment facility may be too great. Another relatively new disposal method for leachate is land application. There are currently eight land application systems in Minnesota. Some sort of pre-treatment of leachate such as a pond system or mechanical pre-treatment is required before it can be land applied. The leachate is spray irrigated over a number of sites that have suitable soils, are a sufficient distance from water supply wells and have enough separation from ground water. Eventually the limit is reached on the amount of metals and salts the soils can hold, and another site must be selected. Since the metals are inorganics and are not broken down, they may be taken up by plants or stick to the soil particles, but they do not disappear.
Compost Facilities
The MSW compost facilities in Minnesota have, at times, had difficulty selling or even giving away finished compost. Frequently the problem has been that the level of the regulated metals (including the four listed metals) has pushed the compost into the restricted use, Class II classification. Very little, if any, of the MSW compost produced in the state has been Class I compost. The solid waste rules pertaining to compost were recently revised, but the standards, particularly for lead, will still prove problematic for facility operators.
Incineration
Metals, which under normal landfill conditions might not leach, may be released to the environment when burned in an incinerator. Of the products affected by the Toxics statute, this is particularly true with plastics. Heavy metals cannot be destroyed in an incinerator. They must exit or accumulate within the unit. Most of the metals will remain in the bottom ash, a portion become gases and exit with the flue gases. The metals may attach themselves to the particulate matter in the flue gases and some will be captured in the flue gas cleaning equipment.
The type of air pollution control systems used by the facility also affects the efficiency of removal of heavy metals from flue gasses. Electrostatic precipitator (ESPs) use a series of high voltage discharges to create negatively charged ions to attract the positively charged fly ash particles. Removal efficiency for cadmium ranged from 76 percent to 96.5 percent in facilities in Minnesota for which there is data available. Chromium ranged from 67 percent to 96.1 percent and lead ranged from 74.5 percent to 99.5 percent. Acid gas scrubbers add efficiency to an air pollution control system as well. In general, ESPs are not as efficient at removing ash particles as a fabric filter in combination with a spray drier or dry sorbent injection system. Efficiencies for those generally range from 99 percent for lead, and cadmium, to 90 percent to 99 percent for chromium.
Control of mercury during incineration is the exception. Most metals condense to form solid particles as flue gas is cooled so that they can be collected as particulate matter. Mercuric chloride and elemental mercury are released during incineration of MSW. Because MSW facilities must operate their ESPs at temperatures where mercury remains as a gas, ESPs are especially inefficient at removing mercury, in some cases not removing any.
The best combination for effective mercury capture appears to be operating the control devices at low temperatures and maintaining a high level of carbon in the fly ash. This can be done by retrofitting incinerators with equipment that reduces flue gas temperatures, and injecting activated carbon into the cool flue gas stream. Activated carbon injection can remove at least 85 percent of mercury in the flue gas, and at some facilities can remove greater than 95 percent of the flue gas mercury.
MSW incinerators in 1990 emitted an estimated 1,497 pounds of mercury in Minnesota or 19 percent of the total emissions. Minnesota MSW incinerators are required to retrofit their facilities by mid-2000 to incorporate temperature control and activated carbon injection to comply with state and federal rules. Once this equipment is operating, mercury emissions are expected to be below 553 pounds per year.
MPCA Listed Metals Program Conclusion
Decreased funding has required the MPCA to reduce its workforce by nine percent by the end of fiscal year 2003. This also caused the agency to rethink its organizational structure, including eliminating and reducing some programs. As a result, the Listed Metals program has been concluded.
Program progress and key accomplishments
At its January 18, 2001 meeting, the Listed Metals Advisory Council completed its review of all specified products. The following are key accomplishments of the program:
- The Council used an open, fair and legal process for all product reviews and decisions at its monthly meetings.
- The Council completed its review of all 229 products five years ahead of schedule, saving the state and regulated community approximately $500,000 in program administrative costs.
- The Council recommended that the MPCA commissioner ban 22 products. This resulted in an estimated annual reduction of 88,600 pounds of listed metals in Minnesota. Additional listed metal reductions in Minnesota were realized by the voluntary discontinuation of other products containing listed metals.
- The Council produced a large public legal record to support its decisions. This record may also provide technical information for MPCA and other programs.
The MPCA has begun rulemaking to make permanent the product bans recommended by the Council and approved by the commissioner. Since the Council has completed its review of all specified products, the only funds needed for the program are those for the development of rules. The rulemaking will be completed by the end of FY2002.
Additional information about concluding the Listed Metals Program is available in the following fact sheet:
Listed Metals in Specified Products
