"Published Occasionally at Irregular Intervals"
~ Dr.
Arthur L. Craigmill ~
Extension
Toxicologist
Measuring Exposure to an Elemental Mercury Spill - Dakota County, Minnesota, 2004
~~ TOXICOLOGY TIDBITS ~~
Everything You Ever Wanted to Know About Eggs
~~ VET NOTES ~~
Outbreak of Multidrug-Resistant Salmonella Typhimurium Associated with Rodents Purchased at Retail Pet Stores
As part of its epidemiologic investigation, MDH staff interviewed some of the youths the morning after the event and learned that the teenagers had attempted to ignite the mercury and might have been exposed to fumes. Subsequent sampling with the mercury vapor analyzer in motel rooms of displaced families revealed mercury contamination, and high concentrations of mercury vapor found near the hair of three youths 24 hours after exposure suggested that exposures might have been more severe than initially indicated, that decontamination was incomplete, and that exposures were continuing. Consequently, 14 youths aged 6-16 years with known exposures were examined by physicians; 11 were evaluated at a hospital in St. Paul, Minnesota.
Editorial Note: Exposure to elemental mercury occurs largely from inhaling mercury vapors; very little mercury is absorbed through the skin or by ingestion. Mercury spills pose a serious health hazard and are difficult to clean because most common methods (e.g., sweeping or vacuuming) disperse mercury, increasing the surface area of the mercury, increasing evaporation, and exacerbating the contamination. This report illustrates that use of real-time portable instruments such as mercury vapor analyzers can enable investigators to rapidly measure mercury vapor concentrations and determine the extent of an exposure incident.The half-life of total mercury in blood for persons exposed to
mercury vapor is 2-5 days, reflecting distribution to tissues and
elimination through exhalation, which corresponds to the results in
this report; blood mercury levels were below the detection limit 7-13
days after initial positive measurement. Exhaled mercury concentrations
have been found to decrease, with half-lives of 13-25 hours and 1.6-2.3
days. These half-lives also are consistent with the results in this
report. However, exhalation half-lives longer than 30 hours might
indicate continuing exposure or reexposure to mercury. The patient with
the calculated half-life of 44 hours had been reexposed on day 4.
Exhaled vapor concentrations can also depend on proper exhalation by
patients. To compare data between patients, investigators should
instruct all patients to exhale in the same manner; however, mercury
vapor half-lives are repeated measures and will not be as sensitive to
individual differences. The lack of correlation between exhaled mercury
and blood mercury is likely caused by measurement of different forms of
mercury (i.e., total mercury for blood and mercury vapor for exhaled)
and the small range of exposures.
Approximately 70%-80% of inhaled mercury enters the blood before distribution to tissues; the rest is immediately exhaled. An estimated 7% of retained mercury is exhaled in the first 3 days after exposure. Approximately 9.2% and 2.4% is excreted in feces and urine, respectively, within 7 days. Conversely, mercury concentrations in blood can increase rapidly after an acute exposure to mercury, providing timely indication of exposure. In addition, the short half-life of mercury in blood can enable confirmation of the cessation of exposure. However, investigators should be aware of potential confounders to measurements of mercury concentrations (e.g., fish consumption, dental amalgams, medicinal use, and ritualistic use of mercury such as sprinkling on a floor for good luck).
In this report, the experiences of responders and investigators also underscore several recommendations for demolition and waste-disposal companies and government agencies. These include 1) securing elemental mercury at demolition sites, 2) confirming mercury decontamination by sampling, 3) providing sensitive field instruments and appropriate training for tracking mercury contamination and exposure, and 4) incorporating quality-assurance controls into all data collection activities.
REF: MMWR, February 18, 2005, 54(06).
Editorial Note: This report describes three outbreaks in the United States and Canada in which Roma tomatoes were implicated; as a result of these outbreaks, 2004 had the highest number of recorded annual tomato-associated Salmonella infections.
Salmonella can enter tomato plants through roots or flowers and can enter the tomato fruit through small cracks in the skin, the stem scar, or the plant itself. However, whether Salmonella can travel from roots to the fruit, or if seeds can contaminate subsequent generations of tomato plants, is unknown. Understanding the mechanism of contamination and amplification of contamination of large volumes of tomatoes is critical to prevent large-scale, tomato-associated outbreaks. Contamination might occur during multiple steps from the tomato seed nursery to the final kitchen. Eradication of Salmonella from the interior of the tomato is difficult without cooking, even if treated with highly concentrated chlorine solution.
Public health professionals should be aware of tomatoes as a
possible
vehicle when investigating Salmonella outbreaks. Current
knowledge
of mechanisms of tomato contamination and methods of eradication of Salmonella
in fruit are inadequate to fully define interventions that will ensure
produce safety. Studies into these concerns should be a priority for
the agricultural industry, food safety agencies, and the public health
community.
REF: MMWR, April 8, 2005, Volume 54, No. 13
EPA is initiating the Drinking Water Lead Reduction Plan to strengthen,
update and clarify existing requirements for water utilities and states
to test for and reduce lead in drinking water. This action, which
follows extensive analysis and assessment of current implementation of
these regulations, will tighten monitoring, treatment, lead service
line management and customer awareness. The plan also addresses lead in
tap water in schools and child care facilities to further protect
vulnerable populations. Lead is a
highly toxic metal that was used for many years in products found in
and around homes. Even at low levels, lead may cause a range of health
effects including behavioral problems and learning disabilities. Children
six years old and under are most at risk because this is when the brain
is developing. The primary source of lead exposure for most children is
lead-based paint in older homes. Lead in drinking water adds
to that exposure.
Drinking water does not start
out containing lead. Lead is picked up as water passes through pipes
and household plumbing fittings and fixtures that contain lead. Water
leaches lead from these sources and becomes contaminated. In 1991, to
reduce lead in drinking water, EPA issued the LCR. The LCR requires
water utilities to reduce lead contamination by controlling the
corrosiveness of water and, as needed, replace lead service lines used
to carry water from the street to the home.
Under the LCR, if 10 percent of required sampling show lead levels
above a 15 parts per billion (ppb) action level, the utility must 1)
take a number of actions to control corrosion and 2) carry out public
education to inform consumers of actions they can take to reduce their
exposure to lead. If lead levels continue to be elevated after
anti-corrosion treatment is installed, the utility must replace lead
service lines.
Because virtually all lead
enters water after it leaves the main system to enter individual homes
and buildings, the LCR is the only drinking water regulation that
requires utilities to
test water at the tap. This also means that individual homes will have
different levels of lead in their tap water due to the age or condition
of pipes,
plumbing materials and fixtures or other factors. For this reason,
customer
awareness and education are important components of the LCR and state
and
water utilities lead reduction programs.
EPA plans to propose regulatory changes to the LCR
in the following areas by early 2006:
In addition, the agency
will convene a workshop in mid-2005 to discuss actions that can be
taken to reduce the lead content of plumbing fittings and fixtures. EPA
will also promote research in key areas, such as alternative approaches
to tap monitoring and
techniques for lead service line replacement.
More
information on National Review of LCR Implementation and Drinking Water
Lead Reduction Plan is available online at: http://www.epa.gov/safewater/lcrmr/lead_review.html. Information about lead in drinking water is available
online at: http://www.epa.gov/safewater/lead or by calling the Safe Drinking Water Hotline at
1-800-426-4791. Information about lead around the home is available
online at: http://www.epa.gov/lead or from EPA's National Lead Information Center (NLIC)
at 1-800-424-LEAD (5323).
REF: EPA
News Release, March 7, 2005.
The studies described in this report represent the first efforts to quantitate human exposure to MC pesticides during large-scale MC activities. Two of these studies used a prospective crossover design that compared urine metabolite concentrations after ULV spraying of pesticides with baseline concentrations. Use of sensitive analytic methods in these studies indicated that the urine pesticide metabolite concentrations measured were low (parts per billion). The concentration of urine metabolites in these studies are comparable with those measured in the general population. In addition, these three studies did not indicate an overall increase of pesticide metabolite concentrations in the urine of participants after spraying during MC activities. The concentrations of naled, permethrin, and d-phenothrin during emergency ULV applications might be too low to cause important human exposure.
In certain participants, investigators found an association between
home and/or work application of pesticides and pesticide metabolite
concentrations. The concentrations in participants who had histories of
exposure were within the range of the general U.S. population. These
findings are consistent with occupational studies in which prolonged
exposure to pesticides through several hours of work in plant nurseries
and greenhouses was associated with low but measurable concentrations
of urine pesticide metabolites. These findings also are compatible with
a prospective study that quantitated higher 3-phenoxybenzoic acid
concentrations in the urine of pest-control operators 1 day after
spraying pyrethroids.
Aerial spraying with ULV naled and truck-mounted spraying with
permethrin/d-phenothrin were not associated with an increase in urine
pesticide metabolite concentrations among residents of these rural,
suburban, and urban communities. These findings suggest
that ULV application of naled, permethrin, and d-phenothrin is safe to
humans as part of integrated vector control. The findings are
noteworthy because ULV applications of pesticides that kill adult
mosquitoes are an important tool in the public health response to WNV. Future
studies should address the long-term safety of low-concentration
exposure to naled and synthetic pyrethroid applications. In addition,
public health interventions might be needed to reduce home and
workplace exposure to pesticides.
Lindane is an organochlorine pesticide found in certain prescription-only shampoos and topical lotions used to treat pediculosis (i.e., lice infestation) and scabies; lindane has been associated with human neurologic toxicity. In 2004, CDC was alerted to cases of illness caused by unintentional ingestion of lindane by persons mistaking the product for a liquid oral medication (e.g., cough syrup). To assess the extent of illness from ingestion of lindane, CDC, with assistance from the U.S. Environmental Protection Agency, Food and Drug Administration (FDA), and state health departments, collected case reports and analyzed data from the Sentinel Event Notification System for Occupational Risks-Pesticides (SENSOR-Pesticides) program and the Toxic Exposure Surveillance System (TESS). This report summarizes the results of that analysis, which identified 870 cases of unintentional lindane ingestion during 1998-2003, and describes two examples of lindane ingestions. To reduce the risk of lindane ingestion, public health authorities should alert clinicians to the hazards of lindane and the importance of following FDA usage guidelines, which include dispensing lindane in manufacturer-produced, 1- or 2-ounce single-use containers.
Case ReportsCase 2. In December 2003, a man aged 47 years in Texas
mistakenly ingested 1 ounce of lindane (percentage concentration
unknown) from a bottle he believed to be cough syrup. The man vomited;
he contacted the poison control center the following morning. He did
not seek clinical evaluation.
Before the advisory, bottles of bulk lindane were sometimes repackaged by pharmacies into smaller bottles resembling those used for liquid oral medications (e.g., cough syrup). This resemblance likely contributed to many unintentional ingestions. Subsequent to the advisory, bottles of bulk lindane still in use were not recalled from pharmacies. Therefore, some repackaging might still occur. In addition, consumers might have repackaged lindane in their homes.
In September 2004, the North American Task Force on Lindane drafted an action plan for future use. On January 1, 2005, Canada withdrew registration of lindane for agricultural pest control; Mexico is working on a plan to phase out all uses of lindane. However, with the exception of California, which banned lindane for medicinal use on January 1, 2002, U.S. representatives to the North American Commission for Environmental Cooperation announced that the United States will continue to allow use of lindane as both a pesticide and pharmaceutical.
REF: MMWR, 54(21), June 3, 2005.
TOXICOLOGY TIDBITS The Food and Drug Administration (FDA) is advising that some soft cheeses made with raw milk present a health risk, especially to high risk groups, such as pregnant women, newborns, older adults, and people with weakened immune systems. Such raw milk soft cheeses can cause several serious infectious diseases including listeriosis, brucellosis, salmonellosis and tuberculosis. Recently, cases of tuberculosis in New York City have been linked to consumption of queso fresco style cheeses, either imported from Mexico or consumed in Mexico, contaminated with Mycobacterium bovis, the causative agent.
The raw milk soft cheeses of most concern can originate from Mexico and Central American countries. Queso fresco style cheese, which is soft and white, has been found to be the most popular kind of cheese among the Hispanic community and can include Queso Panela, Asadero, Blanco and Ranchero, among other styles and may be imported or produced in the U.S.
FDA recommends that consumers do not eat any unripened raw milk soft cheeses from Mexico, Nicaragua, or Honduras. Data show that they are often contaminated with pathogens. FDA further recommends that consumers not purchase or consume raw milk soft cheeses from sources such as flea markets, sellers operating door-to-door or out of their trucks or shipped or carried in luggage to them from Mexico, Nicaragua, or Honduras. This includes cheeses made at home by individuals.
FDA further advises that there is some risk of
infection from a number of pathogenic bacteria for anyone who eats raw
milk soft cheese from any source.
Clarification: On March 14th, FDA issued a raw milk soft cheese advisory that mentioned a number of cheeses, including "Ranchero." We've become aware that "Ranchero" is a trademark of the Cacique company, in Industry, California. Cacique's "Ranchero" is made with pasteurized milk. The milk cheese advisory was not intended to include this specific product.
REF: FDA STATEMENT, March 14, 2005 http://www.fda.gov/bbs/topics/news/2005/NEW01165.html
"This is a critical time for mosquito
prevention,"
Jackson said. "Residents should eliminate standing water around their
homes
where mosquitoes might breed, keep their pools in good working order
and
report dead birds."
As of March 17th, 32 dead birds from the following counties have
tested positive for WNV: Alameda, Contra Costa, El Dorado, Fresno,
Humboldt, Kern, Kings, Los Angeles, Orange, Placer, Sacramento, Santa
Clara, Santa Cruz,
Solano, Sonoma, Stanislaus, Tulare and Yolo counties. WNV has also been
detected
in a sentinel chicken in San Bernardino County and mosquitoes in Orange
County.
The public can report dead birds to the California Department of Health Services by logging on to www.westnile.ca.gov or phoning toll-free 1-877-WNV-BIRD.
"Early detection is the key to preventing the
spread of West Nile virus," Jackson said. "We anticipate that there
will be an
increase in West Nile virus activity in Northern and Central California
this year. "
Jackson also urged all horse owners to consult
their veterinarians about proper and timely WNV vaccinations for their
animals. In 2004, 540 equine WNV infections were reported statewide,
most of which involved horses that were not vaccinated.
"Although California experienced widespread West
Nile virus transmission last year, we believe that the number of human
cases
would have been greater without the aggressive control measures
conducted
by state and local agencies," Jackson said. "Personal protection
measures
taken by the public last year were significant in minimizing illness
and
death from West Nile virus. I urge all residents to be vigilant in
avoiding
mosquito bites."
Last year, there were a total of 829 human WNV infections, including 27 deaths, reported from 23 counties in California. The virus was detected in all 58 counties.
For more information about WNV or to report dead birds, visit www.westnile.ca.gov.
VETERINARY NOTES Minnesota. During August 2004, a boy aged 5 years had diarrhea of 14 days' duration (initially bloody), abdominal cramps, vomiting, and fever (103ºF [39.4ºC]). A stool culture yielded S. Typhimurium. Four days before the boy became ill, his family had purchased a mouse from a retail pet store supplied by a Minnesota distributor. The mouse became lethargic and had diarrhea immediately after purchase. Even though the mouse was ill, the boy frequently handled and kissed the mouse. One week after purchase, the mouse died; the mouse was frozen and later submitted for testing at MDH. Cultures of the mouse's lungs, pooled liver and spleen, and intestines yielded growth of S. Typhimurium, with a pulsed-field gel electrophoresis (PFGE) pattern indistinguishable from the boy's isolate.
On August 30, a veterinarian for the Minnesota pet distributor called MDH about isolation of Salmonella from two ill hamsters submitted to the University of Minnesota Veterinary Diagnostic Laboratory (UMVDL). The hamsters were part of a shipment of 780 received on August 1 from an Iowa pet distributor. A total of 243 hamsters from this shipment were subsequently sent from the Minnesota distributor to 15 retail pet stores in four midwestern states. Distribution of rodents from the Minnesota distributor ceased on August 23 after numerous hamster deaths. Diarrhea was present in the majority of ill hamsters. By August 29, approximately 320 (60%) of the remaining 537 hamsters at the Minnesota distributor had died; the other hamsters were euthanized.
Based on recognition of the Minnesota and South Carolina human
cases,
CDC and MDH conducted a national search for additional human cases
associated with exposure to rodents. A review of isolates submitted to
the PulseNet
National Salmonella Database in 2004 revealed 28 matching human
case-isolates of S. Typhimurium from 19 states; patient illness
onset dates ranged from December 2003 to October 2004. Of 22 patients
interviewed, 13 (59%)
had been exposed to rodents purchased from retail pet stores; all
exposures
occurred during the 8 days before illness onset. Two (9%) patients
acquired
salmonellosis through secondary exposure. Seven (32%) of the 22
patients
had no identified rodent exposure. Four patients remained under
investigation,
and two were lost to follow-up.
Cases described in this outbreak were dispersed temporally and geographically, and rodent purchases occurred through multiple retail pet store chains and pet distributors; these factors might reflect the geographic spread of S. Typhimurium from a common source of infection occurring earlier in the chain of pet distributors or breeders. The recovery of S. Typhimurium from reusable transport containers, cages, and bins contaminated with rodent droppings offers a potential mechanism for both the environmental persistence and geographic spread of Salmonella. Rodents subsequently transported or housed in contaminated containers might have been exposed to Salmonella and become infected without direct contact with infected rodents.
Consumers and animal workers should be aware that rodents,
like reptiles, can shed Salmonella; therefore, they should
expect rodent feces to be potentially infectious. Salmonella
transmission to humans can be reduced by thoroughly washing hands with
soap and water after handling rodents or their cages or bedding. Young
children who are unable to reliably wash their hands should avoid
contact with rodent feces. Additional public health
recommendations for preventing salmonellosis from reptiles might also
be appropriate for preventing salmonellosis from pet rodents.
REF: MMWR, 54(17), May 6, 2005
