Transcript B2B_Occupational__Environmental_health M Afanasyeva 2015

Back to Basics, 2015
POPULATION HEALTH:
Environmental & Occupational Health
Marina Afanasyeva, MD, MPH, PhD (PGY3)
Public Health & Preventive Medicine
Residency Program
Based on the previous lectures by Drs. M. Maher, B. Pinard, G. Dunkley, R. Spasoff, and N. Birkett
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MCC Objectives: Population Health
78-6 Environment
Rationale:
• Environmental issues are important in medical practice because
exposures may be causally linked to a patient's clinical presentation and
the health of the exposed population. A physician is expected to work
with regulatory agencies and allied health professionals (e.g.,
occupational hygienists), where appropriate, to help implement the
necessary interventions to prevent future illness. Physician involvement
is important in the promotion of global environmental health.
© The Medical Council of Canada, 2015
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MCC Objectives: Population Health
78-6 Environment
Key Objectives:
• Recognize the implications of environmental hazards at both the
individual and population level.
• Respond to the patients concerns through appropriate information
gathering and treatment.
• Work collaboratively with local, provincial and national
agencies/governments as appropriate to address the concerns at a
population level.
• Communicate with patients, communities, and employers, where
appropriate, concerning environmental risk assessment
© The Medical Council of Canada, 2015
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MCC Objectives: Population Health
78-6 Environment
Enabling objectives
• Identify common environmental hazards and be able to classify them into the
appropriate category of chemical, biological, physical and radiation.
• Identify the common hazards that are found in air, water, soil and foods.
• Describe the steps in an environmental risk assessment and be able to critically
review a simple risk assessment for a community.
• Conduct a focussed clinical assessment of exposed persons in order to
determine the causal linkage between exposure and the clinical condition.
• Be aware of local, regional, provincial and national regulatory agencies that can
assist in the investigation of environmental concerns.
• Describe simple interventions that will be effective in reducing environmental
exposures and risk of disease (e.g. sunscreen for sunburns, bug spray for
prevention of West Nile Virus infection).
• Communicate simple environmental risk assessment information to both
patients and the community.
© The Medical Council of Canada, 2015
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Environmental Hazards
• Environmental exposure:
– Natural and human-made environment
– Reservoirs: air, water, soil, food
– Route: inhalation, ingestion, absorption
– Exposure setting:
• Workplace: occupational health (high level exposure,
acute or chronic)
• Outside workplace: environmental health (low level
exposure, chronic)
March 2015
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Hazards in Air
Physical contaminants
• Radiation: Radon (lung cancer), UV (skin cancer)
• Sound waves (hearing loss)
Chemical contaminants
• Ozone at ground level (worsens asthma)
• Sulphur dioxide (SO2); nitrogen dioxide (NO2)
(respiratory irritants)
• Carbon monoxide (CO) (asphyxiation, headache)
• Organic compounds: benzene (carcinogen – leukemia)
• Second-hand tobacco smoke (lung cancer)
• Heavy metals; industrial emissions
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Hazards in Air
Biological contaminants:
• Bacteria: Legionella pneumophila (Legionnaires’
pneumonia, Pontiac fever)
• Dust mites (upper and lower-airway Sx)
• Moulds (allergies)
• Particulates (pollen, spores, aerosols) (allergies,
asthma)
Global warming-related:
• Extreme weather (heat waves), change in distribution
of vectors of disease, crop failures, etc.
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Hazards in Water
Biological agents:
• Bacteria: E. coli, Salmonella, Pseudomonas
• Protozoa (cysts): Giardia, Cryptosporidium (GI
symptoms mainly)
• Blue green algae (skin irritation, GI symptoms)
• Higher risk: Aboriginal Canadians, rural population
Chemical agents:
• Volatile organic compounds (VOC), pesticides, heavy
metals, other waste from industries (effects depend on
contaminant)
• Chlorination by-products - trihalomethanes (THM)
(cancer)
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Hazards in Soil
Chemical agents:
• Pesticides, petroleum hydrocarbons, solvents, motor
oil, lead (effects depend on contaminant)
• Higher risk: infants/toddlers
Biological agents:
• Bacteria (tetanus)
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Hazards in Food
Biological Contaminants
• Norovirus (gastroenteritis)
• Campylobacter - raw poultry (diarrhea, maybe bloody)
• Salmonella - raw eggs, poultry, meat (diarrhea, maybe
bloody)
• E. coli - hamburger meat (diarrhea, HUS)
• Listeria monocytogenes (listeriosis)
• Clostridium botulinum (botulism)
• Parasites; aflatoxin; prions (BSE)
Chemical Contaminants
• PCBs, dioxins/furans, pesticide residues (DDT), mercury
• Food additives: nitrites, sulfites (allergy)
• Drugs given to livestock: antibiotics, hormones
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Environmental Risk Assessment
Process of evaluating the likelihood of occurrence
and probable severity of health effects due to a
hazard
Done by: occupational health agencies,
environmental protection agencies, public health
authorities, clinicians
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Health Risk: The interaction of
Hazard, Exposure, and Susceptibility (3 necessary
components)
Exposure
Hazard
Risk
Susceptibility
Individual
characteristics
Steps in Risk Assessment
1. Hazard identification: Is an environmental hazard
involved? What is it?
2. Risk characterization: Is the hazard likely to cause
these types of symptoms in this type of patient?
3. Exposure assessment: Is the patient’s exposure
enough to cause these symptoms?
4. Risk estimation: How much has the hazard
contributed to the patient’s condition?
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Steps in Risk Assessment (II)
• Hazard Identification:
Is an environmental hazard involved? What is it?
– Identified the agent capable of causing
– Adverse effects
– in the susceptible target population
– Under certain condition of exposure
– Involves a thorough environmental Hx (to be discussed)
• Risk characterisation:
Can this hazard cause these symptoms?
– Describe the potential health effects of hazard
– Sources of info: scientific literature, toxicology or poison
center, public health department
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Risk Characterisation
• Workplace Hazardous Material Information
System (WHMIS):
– Labeling requirements for hazards
– Indicates availability of Materials Safety Data
Sheets (MSDS): more details on hazard, how to
handle it, what to do if emergency
– MSDS are available on the web – should find one
site and bookmark it (Health Canada): http://www.hcsc.gc.ca/ewh-semt/occup-travail/whmis-simdut/index-eng.php)
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Exposure Assessment
(of individual or population)
 Estimated from history (most of the time) and/or
inspection of environment
 Measured directly (sometimes)
– in environment
– In human samples (blood lead level)
 Affected by route, site, duration, frequency
Consultants: environmental medicine specialists (eg. at Public Health
Ontario), toxicologists, industrial/occupational hygienists (eg. at the
Ministry of Labor, see http://www.crboh.ca)
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Final Step in Risk Assessment:
Risk Estimation
 Probability of a health effect and its severity
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Dosis facit venenum
• What is there that is
not poison? All things
are poison and
nothing without
poison. Solely, the
dose determines that
a thing is not a poison.
– Paracelsus (1493-1541)
Adopted from the lecture by Michael A. Trush.
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Toxicokinetics
• What happens to the toxin!
• Time course of toxicants in the body during
the processes of absorption, distribution,
biotransformation, and excretion (or storage)
or clearance.
• The end result of these toxicokinetic processes
is a biologically effective dose of the toxicant.
• It is a part of the exposure assessment
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Toxicodynamics
• What happens to the human body!
• The molecular, biochemical, and physiological
effects of toxicants or their metabolites in
biological systems
• It is a part of the risk estimation
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Focused Environmental History
 Clues to environmental causes
 Detailed environmental history
 A part of hazard identification and exposure
assessment
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Clues to Environmental Causes
• Clues that illness is caused by environmental
factors:
– Patient suspects it
– Pattern of illness atypical (absence of usual risk
factors, unusual age group, course of illness
unusual, no response to tx)
– Temporal pattern of illness (weekends/weekdays,
holidays/home)
– No obvious other cause
– Signs/symptoms suggest specific toxins
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CH20PD2
Environmental history - CH20PD2:
• Community: neighborhood sources of hazard; industry, waste
storage
• Home: year of construction, renovations; materials used in
construction and decoration; moulds; garden and house plants; use
of cleaning products, pesticides, herbicides
• Hobbies and leisure: exposure to chemicals, dusts, or microorganisms
• Occupation: current and previous occupations; longest occupation;
work with known hazards; air quality
• Personal habits: hygiene products; smoking
• Diet: sources of food and water; cooking methods; food fads
• Drugs: prescription, non-prescription, and alternative medications;
health practices
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Focused Environmental History
• If a scanning question reveals a possible hazard, ask detailed
questions about the nature and level of the hazard and then
check:
• Time: When did symptoms begin? When did exposure begin?
When do symptoms get worse? When do they improve?
• Place: Where is the patient when symptoms get worse?
Where is the likely hazard? What is the channel through
which the hazard reaches the patient?
• Person: Does anyone else have similar symptoms? Who?
When? Where?
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Regulatory Agencies
• If evidence or a strong suspicion exist for a
causal connection between exposure and the
clinical presentation, notify the appropriate
authorities to inspect the site and thereafter
to decrease and eliminate exposure.
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Environmental Health Jurisdiction
– Public Health Unit
• Enforcement of water and food safety regulations, sanitation, local hazard
assessment, reportable diseases
– Municipal
• Garbage disposal, recycling
– Province/territory
• Toxic waste disposal, air/water standards
• Ontario Ministry of the Environment (monitors air quality across ON)
– Federal
• Food regulations (Health Canada), designating and regulating toxic substances
• The Asbestos Mines and Mills Release Regulations (Environment Canada)
– International
• Multilateral agreement (Kyoto Protocol)
•
When in doubt who to ask, contact your local public health unit.
• Ottawa Public Health (613) 580-6744
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Risk management
• Interventions to reduce environmental exposures:
– Carbon monoxide: CO home detector
– Salmonella: well cooked poultry and eggs, safe food
handling
– Listeria: avoidance of unpasteurized cheese for pregnant
women
– West Nile Virus: bug spray
– UV light: sunscreen, sunglasses, shade, hat, long sleeves
– Radon: ventilation, air exchanger, radon test kits
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Risk Communication
• Important to allow people to understand the
risk and take action to avoid it
• Elements of communication: message,
messenger (meaning), encoding, channel,
decoding, recipient (understanding)
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Risk Communication
• Factors increasing perception of danger:
– Characteristics of exposure:
• Involuntary; not under personal control
• Unnatural; unfamiliar
• No trust in institution involved; media attention
– Characteristics of outcome:
• Catastrophic (not chronic); immediate; irreversible
• Unknown, uncertain outcome, dreaded outcome
• Affect children or identifiable people
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UV Index
WHO, 2002, Global Solar UV Index
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UV Index Specifics
•
•
•
•
•
•
•
The UV Index that is reported as part of the weather forecast is the highest
expected value for the day
UV rays can cause sunburns, eye cataracts, skin aging, and skin cancer (SCC; BCC;
melanoma)
Highest in the early afternoon (about 1:30 PM Eastern Daylight Saving Time in
Southern Ontario) and during the months of June and July
Avoid the mid-day sun (between 11 AM and 4 PM)
If you must be outside, seek shade, wear sunglasses, use sunscreen, if possible
cover up with lightweight clothing and wear a hat
Sunscreen products with SPF 15 are recommended for daily use
Broad spectrum products (protective against UVA and UVB) with SPF30 or higher
are recommended for individuals performing outdoor work, sports, or recreational
activities
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Air Quality Health Index
• New public health information tool developed
by Health Canada and Environment Canada
• Support decision-making about activity levels
during increased levels of air pollution.
• Calculated based on:
• Ozone (O3) at ground level
• Particulate Matter (PM2.5/PM10)
• Nitrogen Dioxide (NO2)
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Health Risk
Low Risk
Moderate
Risk
High Risk
Air Quality
Health Index
General Population
Enjoy your usual
outdoor activities.
Ideal air quality for outdoor
activities.
4-6
Consider reducing or
rescheduling strenuous
activities outdoors if you
are experiencing
symptoms.
No need to modify your
usual outdoor activities
unless you experience
symptoms such as coughing
and throat irritation.
7-10
Reduce or reschedule
strenuous activities
outdoors. Children and
the elderly should also
take it easy.
Consider reducing or
rescheduling strenuous
activities outdoors if you
experience symptoms such
as coughing and throat
irritation.
Avoid strenuous
activities outdoors.
Children and the elderly
should also avoid
outdoor physical
exertion.March 2013
Reduce or reschedule
strenuous activities
outdoors, especially if you
experience symptoms such
as coughing and throat
irritation.
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1-3
Above 10
Very High
Risk
At Risk Population
Occupational Medicine
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MCC Objectives:
78-8 Work-Related Health Issues
• Key Objective:
• Given a patient with a health problem, the candidate
will evaluate the possible workplace etiological
factors, to assess the contribution of occupational
exposures for the most common pathologies, to
assess the impact of the condition on the ability to
work, and develop an appropriate management plan.
Particular attention should be paid to the
identification of occupational risks for the patient
and his/her co-workers.
© The Medical Council of Canada, 2015
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MCC Objectives
Causal Conditions (list not exhaustive)
• Ergonomic hazards
– e.g. awkward postures and movements, poor lighting
• Chemical hazards
– e.g. organic solvents, metals, asbestos, toxic gases
• Physical hazards
– e.g. noise, vibration, radiation
• Biological hazards
– e.g. blood or other body fluids, animal and bird droppings
• Psychological and work organization hazards
– e.g. workplace stressors, workplace bullying
© The Medical Council of Canada, 2015
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Occupational Medicine (OM) in MCCQE Part 1
• As a primary question
• Integrated into options for other questions
• Think about classic occupational skin and lung issues
• Also think about other domains in which OM can play a role,
such as psychiatry, and also specific conditions which have
occupational causality such as abnormal liver function tests,
fatigue, hypertension etc.
• For a sampling of “hot topics” in OM, go to the Scientific
American website and type Occupational Medicine in the
search box
Types of clinical scenarios that may involve
occupational exposure
•
•
•
•
•
•
•
•
•
•
•
•
•
•
•
Cough
Hand and wrist injuries
Numbness / tingling / altered sensation
Fatigue
Allergic reactions and atopy
Altered hemoglobin levels
Syncope and pre-syncopy
Dysmenorrhea
Proteinuria
Sleep disorders
Bone or joint injury
Back pain
Neck pain
Poisoning
Prenatal Care
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Occupational Health as a Public Health Concern
•Most of the world’s population (58%) spend 1/3 of their adult
life at work (WHO 1994)
•In Canada
• 920 work place deaths in 2001
• 373,216 lost-time injuries in 2001
• 1 of 68 employed workers in 2010 was injured or harmed on the job
and received workers compensation as a result.
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Categories of occupational hazards
1. Physical:
heat, cold, vibration, noise, air
pressure, radiation
2. Chemical:
organic solvents (carbon
tetrachloride), mineral dusts (silica,
asbestos), heavy metals, gases,
pesticides, second-hand smoke
3. Biological:
bacteria, viruses (exposure to blood),
mold
4. Ergonomic (mechanical):
force, posture, repetitive strain
5. Psychosocial:
psychotraumatic events, high demand
low control, lack of support
All impact upon the well-being, working capacity and even
the life span of working individuals
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Occupational Health Outcomes
• The most significant chemical exposures tend to be solvents
and heavy metals:
– Most solvents cause CNS depression, irritation and
dermatitis
– Some solvents causes PNS, hepatic and/or renal toxicity
– Heavy metals primarily cause CNS, PNS, haem, and renal
toxicity
This material is courtesy of Aaron Thompson, MD, MPH, FRCPC
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Occupational Health Outcomes
• Many chemical and biological exposures can cause
allergy resulting in:
– Asthma
– Allergic Contact Dermatitis
This material is courtesy of Aaron Thompson, MD, MPH, FRCPC
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Occupational Health Outcomes
• Approximately 10% of all cancers are occupational
– Common occupational cancers are lung, bladder,
and mesothelioma
– Common occupational carcinogens are asbestos,
polyaromatic hydrocarbons (PAHs), and aromatic
amines
This material is courtesy of Aaron Thompson, MD, MPH, FRCPC
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Asbestos
• Pulmonary fibrosis (asbestosis) – exertional dyspnea and
bibasilar end-inspiratory rales
• Pleural abnormalities (localized and diffuse pleural
thickening, rounded atelectasis), mesothelioma, and lung
cancer, and it may be associated with cancer at some
extra-thoracic sites
• Most important route of exposure is inhalation
• Miners, shipbuilding facility workers, demolition worker
• Asbestos in the air adheres to work clothing, even if the
clothes are brushed
• Cleaning of clothes at home liberates asbestos fibers and
has been shown to cause cancer in family members
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Work-related health issues: prevention
• Primary prevention
– Preventing the onset of disease by altering
behaviours or exposures that can lead to disease,
or by protection against the effect of exposure to
a disease agent
– Achieved using hierarchy of controls
•
•
•
•
•
Elimination
Substitution
Engineering
Administrative
Personal Protective Equipment
This material is courtesy of Aaron Thompson, MD, MPH, FRCPC
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Controlling Occupational Risks
Source
Path
Receiver
Potential approaches to risk control
Modify
Redesign
Substitute
Relocate
Enclose
Absorb
Block
Dilute
Ventilate
Enclose
Protect
Relocate
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Work-related health issues: prevention
• Secondary prevention
– Preventing the establishment or progression of a
disease once a person has been exposed to it.
Examples: early detection via screening
procedures that detect disease at an early stage
when intervention may be more cost-effective
– Examples
• Medical Surveillance
• Screening
This material is courtesy of Aaron Thompson, MD, MPH, FRCPC
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Work-related health issues: prevention
• Tertiary prevention
– Preventing the return of a disease that has been
treated in its acute phase. It seeks to limit or
delay the impact caused by the disease on the
patient’s function, longevity, and quality of life.
– Examples
• Disability management
• Return to work
This material is courtesy of Aaron Thompson, MD, MPH, FRCPC
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Work-related health issues: prevention
• 1o prevention
– Minimize Exposure, prevent Outcome
– Approach using hierarchy of controls
• 2o prevention
– Early detection of Outcome
– Screening, surveillance
• 3o prevention
– Mitigate effects of Outcome
– RTW +/- accomodation once effectively treated and
controls have been put into place to prevent recurrence
This material is courtesy of Aaron Thompson, MD, MPH, FRCPC
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1o, 2o, and 3o Prevention
Example: Lead Exposed Worker
• 1o prevention
– Substitute tin for lead
– Enclose process, increase ventilation
– Optimize hygiene – no eating/drinking/smoking, separate clothes,
shower post shift, housekeeping
– Fit tested lead cartridge respirator
• 2o prevention
– Surveillance: annual Hx, physical, CBC, BLL, zinc protoporphyrin (ZPP)
• 3o prevention
– Chelation if indicated
– RTW when BLL acceptable and control measures in place
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Occupational Health Conditions:
Clinical Assessment and Management
• Confirm diagnosis, then address work relatedness
– Work description and occupational profile
– Prior and current exposure to hazards
– Review of relevant workplace materials safety data sheets
(MSDSs)
– Depending on the condition, there are various objective
means to determine work relatedness
• Prescribing return to work (with restrictions if necessary) is
part of the treatment plan
• If unsure, refer! (Occupational Medicine Specialist)
Based on the material from the lecture by Aaron Thompson, MD, MPH, FRCPC53
Medico-Legal Aspects
• Under provincial jurisdiction except for 16 federally
regulated industries (e.g. banks, airports, highway
transport) – Canada Labour Code
– 90% of workers are under provincial jurisdiction
• Ontario: Occupational Health and Safety Act
– Enforced by Ministry of Labour (inspectors)
– Employers
•
•
•
•
must protect health and safety
report workplace illnesses and injuries
accommodate injured/ill workers
pay cost of injury, illness
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Workplace Safety and Insurance
Act (Ontario)
– Establishes WSIB to oversee work-site
injuries/disease
– Funded by employers only
– Non-fault protection but no right to sue
– MD must submit medical report to WSIB; no need
for patient waiver
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“Duties” of the treating physician
– Treat worker and assist in RTW process
– File Worker’s Compensation claims
– Report to Ministry of Labour if designated
substance has resulted in disability
– CMA Policy 2000
• Be knowledgeable of workplace
• Draft clear recommendations
• Make use of available occupational health resources
– Occupational Health Physician assumes lead in
advising on RTW/accommodation
This material is courtesy of Aaron Thompson, MD, MPH, FRCPC
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This material is courtesy of Aaron Thompson, MD, MPH, FRCPC
Parts of the slide are courtesy of Aaron Thompson, MD, MPH, FRCPC and Richard Wells, Ph.D. CRE-MSD, IWH
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Environmental
and Occupational Health
Multiple Choice Questions
for discussion
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1) Which one of the following is not a typical
feature of asbestosis?
a) increased risk of cancer
b) pleural thickening and calcification
c) interstitial fibrosis
d) obstructive pattern on pulmonary function tests
e) none of the above
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The following statements regarding noise are
true EXCEPT:
a) temporary threshold shift recovers following
cessation of noise exposure
b) permanent threshold shift is characterized by a
progressive pattern of hearing loss
c) most cases of permanent threshold shift are
surgically treatable
d) higher frequency noise is more damaging than
low frequency noise
e) none of the above
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The frequencies most necessary for the
understanding of speech extend from about:
a) 20-20 000 Hz
b) 400-4 000 Hz
c) 250-8 000 Hz
d) 100-5 000 Hz
e) none of the above
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Lead exposure typically results in:
a) chronic dermatitis
b) resting and intention tremor
c) extensor muscle weakness
d) arrhythmias
e) cerebellar ataxia
63
Which of the following statements concerning the
Worker’s Compensation Act is true?
a) the worker reserves the right to sue the
employer for negligence
b) funding is provided by the provincial government
c) the worker is guaranteed payment from the first
day of injury/illness if it is deemed to be workrelated
d) the Worker’s Compensation Board is an
independent, private agency
e) none of the above
64
Which of following statements regarding
radiation is false?
a) natural background radiation accounts for about
half of a typical person’s exposure
b) ionizing radiation causes intestinal villi to
become denuded
c) exposure to non-ionizing radiation may result in
cataracts
d) ionizing radiation results in an increased
incidence of neoplasia such as lung and thyroid
e) none of the above
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All of the following statements concerning
occupational health are true EXCEPT:
a) disorders of reproduction are among the top
10 work-related diseases and injuries
b) most workers are covered by both federal and
provincial legislation with respect to workplace
health and safety
c) skin problems and hearing problems together
are responsible for half of WCB claims
d) a complete occupational medical history
includes investigation of the temporal
relationship between symptoms and exposure
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Which of the following statements concerning
exposure to solvents in the workplace is
true?
a) each solvent compound has a specific antidote
that can be used to treat exposure
b) a prominent symptom of solvent exposure is
memory loss
c) some solvents can cause skin dryness and loss
of subcutaneous adipose tissue
d) solvents do not affect the bone marrow
e) all of the above
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All of the following statements about environmental
health are true EXCEPT:
a) levels of toxic agents measured in the
environment may not reflect internal organ
levels
b) the federal government monitors the quality
and types of industrial emissions and toxic
waste disposal
c) sick building syndrome is associated with
Pontiac fever and Legionnaire’s disease
d) all humans have detectable levels of PCBs
e) none of the above is true
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More MCQs
• Here are some more questions that students
can use to test their own knowledge:
http://www.medicine.uottawa.ca/sim/data/Selftest_Qs_Environmental_e.htm
• (The questions contain comments on the
answers, to illustrate why a given response is
not correct)
69
Self-test (1)
• Which one of the following gases is NOT
irritating to the respiratory tract?
a) ozone
b) sulfur dioxide
c) hydrogen chloride
d) carbon monoxide
e) chlorine
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Self-test (2)
• How much radiation is an "average Canadian adult
woman" typically exposed to each year from the
following sources: background dose; one screening
mammography, and one abdominal CT scan?
a) Background 0.1 Sv; mammography 0.5 Sv; CT 1.0 Sv.
b) Background 1.0 Sv; mammography 0.5 Sv; CT 0.1 Sv.
c) Background 1.0 mSv; mammography 50.0 mSv; CT 5.0 mSv.
d) Background 2.0 mSv; mammography 3.0 mSv; CT 10.0 mSv.
e) Background 1.0 mSv; mammography 0.1 mSv; CT 0.1 mSv.
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Resources for your practice
•
MSDS are available on the web – should find one site and bookmark it (Health Canada): http://www.hc-sc.gc.ca/ewhsemt/occup-travail/whmis-simdut/index-eng.php)
•
List of disease reportable to the medical officer of health
https://app06.ottawa.ca/online_services/forms/health/support/professionals/communicable_disease/form_en.pdf
•
Ottawa Public Health 613 580-6744
•
List of regulation by Environment Canada
http://ec.gc.ca/lcpe-cepa/eng/regulations/detailReg.cfm?intReg=56
•
Check your local AQI and refer your patients to this site
http://www.airqualityontario.com/reports/summary.php
•
Occupational Medicine Specialists of Canada
http://www.omsoc.org
•
Case studies in Evironmental Medicine
http://www.atsdr.cdc.gov/csem/csem.html
•
Lange CURRENT Occupational & Environmental Medicine: Fourth Edition Joseph LaDou McGraw Hill Professional, Oct 23,
2006
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