Health Risk Assessment for Rag Pickers QMRA Solid Waste Group Kelly Baker, Firew Lemma, Shrawan Singh
Health Risk Assessment for Rag Pickers
QMRA Solid Waste GroupKelly Baker, Firew Lemma, Shrawan Singh
• Demographics– Mix of men and
women– Adults and Children– Predominantly low
Socio economic status
• End product results in recyclables that can be sold
Pipali-Urban-Tropical climate-Low-income
Aspergillu
s sp.
Bacillus s
p.
Candida sp.
Escheric
hia coli
Klebisiella
sp.
Proteus s
p.
Pseudomonas aeru
ginosa
Salmonella
sp.
Staphylococcu
s aures
0
2
4
6
8
10
Tota
l Con
cent
ratio
n (C
FU/g
)
Concentration of Microbial Indicators in Waste at Dump Sites
Exposure Route: Unprotected Skin
Exposure Route: Eating using Unwashed hands at the Site
Exposure Route: Inhalation of Aerosolized Matter
Aspergillu
s sp.
Bacillus s
p.
Candida sp.
Escheric
hia coli
Klebisiella
sp.
Proteus s
p.
Pseudomonas aeru
ginosa
Salmonella
sp.
Staphylococcu
s aures
0
2
4
6
8
10
Tota
l Con
cent
ratio
n (C
FU/g
)
Concentration of Microbial Indicators in Waste at Dump Sites
Percentage Distribution of Microbial Indicators Isolated from Saliva, Urine, Stool, and/or Nasal
Passages of Rag Pickers
Candida sp.
Escherichia coli
Klebsiella sp.
Psedomonas aeruginosa
Salmonella sp.
Staphylococcus aures
Strept sp.
0%
20%
40%
60%
80%
100%
Rag Pickers
Control
Indi
cato
rs/P
atho
gens
Obs
erve
d
Staphylococcus aereus• Gram +• Environmental ecology
– Resistant to inactivation via UV, desiccation, etc.• Not always pathogenic• Pathogenic forms possess virulence genes encoding toxins that can
adhere to cells and inactivate antibodies, enabling the bacterium to colonize cell surfaces and resist immunological clearance.
• Acute Disease pathology– Skin boils– Respiratory disease (sinusitis)– Gastrointestinal disease via food poisoning
• Infection of 100,000 organisms sufficient to produce enough endotoxin to cause food intoxication
• Antibiotic-resistant forms of pathogenic S. aureus (e.g. MRSA) is a worldwide problem in clinical medicine.
Health Profile of Rag Pickers: Haematological Indicators
Haemoglobin(gdL-1)
Wbc(x 109 L-1)
Haematocrit (%)
Neutrophil (%)
Lymphocytes (%)
Monocytes (%)
Eosinophils (%)
Basophils (%)
0 10 20 30 40 50 60 70
Control
Rag Pickers
Rag Picker Risk Framework
Microbial Concentration
(cfu/g)
Volume of waste per day
(g/day)
Total concentration in
waste/day (cfu/day)
Transfer efficiency by air to mouth (TEHS) * Frequency
breaths/day (ƒHM=1)
Duration of 8-12 hours/day at site * 0.75 kg waste collected/hour * 5
Decay rate (e(-kt))
Infection
Infection
Infection
Dose-response (DR =
dose/person)
CFUw/g * Waste collected/day * total volume* e(-kt) = CFU/day * AWC * PW * ƒOS * TEOS = Ds * DRS
= Ds * ƒHM * TEHM = DM * DRG
Dose ingested hand-to-mouth
in 5 minutes (DO)
Dose inhaled
Dose transferred object to skin in 5
minutes (DS)
Transfer efficiency object to skin (TEOS)
Frequency contact hand-to-mouth (ƒHM)
Transfer efficiency hands - mouth (TEHM)
Area of hand and arm contacting
waste (ACO)
= infection skin = infection gastrointestinal
Probability of wound (PW =
0.8)
Total area of hand/arm with
open wound (AWC)
frequency contact object and skin (ƒOS)
*set to 1 as constant
Concentration Equation
Microbial Concentration
(cfu/g)
Volume of waste per day
(g/day)
Total concentration in
waste/day (cfu/day)
Duration of 8-12 hours/day at site * 0.75 kg waste collected/hour * 5
Decay rate (e(-kt))
CFU/g * Waste collected/day * total volume handled per day * e(-kt) = CFU/day
Where t = ƒ (t | hours at dump site)
CFU/g * 7.5 kg/day * 5 * e(-0.06*t) = CFU (Staphylococcus aereus)/day
Subcutaneous Exposure Dose via Fomite to Skin Wound
Total concentration in
waste/day (cfu/day)
CFU/day * AWC * 0.8 * 1 * TEOS = Ds (Dose through wound on skin)Where AWC = 0.0203 cm2
(AHAND*0.5)+(AARM*0.25)
Dose transferred object to skin in 5
minutes (DS)
Transfer efficiency object to skin (TEOS)
Area of hand and arm contacting
waste (ACO)
Probability of wound (PW =
0.8)
Total area of hand/arm with
open wound (AWC)
frequency contact object and skin (ƒOS)
*set to 1 as constant
CFU/day * AWC * PW * ƒOS * TEOS = Ds (Dose through wound on skin)Where AWC = AW
ACO
Microbial Concentration
(cfu/g)
Volume of waste per day
(g/day)
Duration of 8-12 hours/day at site * 0.75 kg waste collected/hour * 5
Decay rate (e(-kt))
Gastrointestinal Exposure Dose via Hand-to-Mouth
Total concentration in
waste/day (cfu/day)
Dose ingested hand-to-mouth
in 5 minutes (DO)
Dose transferred object to skin in 5
minutes (DS)
Transfer efficiency object to skin (TEOS)
Area of hand and arm contacting
waste (ACO)
Probability of wound (PW =
0.8)
Total area of hand/arm with
open wound (AWC)
frequency contact object and skin (ƒOS)
*set to 1 as constant
Microbial Concentration
(cfu/g)
Volume of waste per day
(g/day)
Duration of 8-12 hours/day at site * 0.75 kg waste collected/hour * 5
Decay rate (e(-kt))
Frequency contact hand-to-mouth (ƒHM)
Transfer efficiency hands - mouth (TEHM)
Ds (Dose through wound on skin) = * 1 * TEHM = DO (Dose Oral)
Ds (Dose through wound on skin) = * ƒHM * TEHM = DO (Dose Oral)
Rag Picker Risk of Subcutaneous and gastrointestinal infection
Microbial Concentration
(cfu/g)
Volume of waste per day
(g/day)
Total concentration in
waste/day (cfu/day)
Duration of 8-12 hours/day at site * 0.75 kg waste collected/hour * 5
Decay rate (e(-kt))
Infection
Infection
Dose-response (DR =
dose/person)
Dose ingested hand-to-mouth
in 5 minutes (DO)
Dose transferred object to skin in 5
minutes (DS)
Transfer efficiency object to skin (TEOS)
Frequency contact hand-to-mouth (ƒHM)
Transfer efficiency hands - mouth (TEHM)
Area of hand and arm contacting
waste (ACO)
Probability of wound (PW =
0.8)
Total area of hand/arm with
open wound (AWC)
frequency contact object and skin (ƒOS)
*set to 1 as constant
Ds (Dose through wound on skin) = * ƒ (DR | µ) = RS (Risk of subcutaneous infection via skin)
Ds (Dose through wound on skin) = * ƒ (DR | µ) = RO (Risk of gastrointestinal infection via mouth)
AssumptionsParameters Value References Hours of working 10 hr/day Ray et al., 2004Waste Handling rate 0.75 kg/hr Ray et al., 2004Total recyclables Handling 7.5 kg/day Ray et al., 2004
Total waste Handling 5 fold Group assumptionMicrobial Decay constant 0.06 Perez-rodriguez, 2013Size of wound 0.0203 cm2 Group decision
Area of hand and arm adult 4510 cm2 EPA, 2011 edi.Proportion of arm exposed 0.25 Group assumption
Proportion of hand exposed 0.5 Group assumption
Probability of having a wound 0.8 Ray et al., 2004
Transfer efficiency - fomite to skin 0.67 cfu/cm2 Lopez, et al., 2013
Transfer efficiency – skin to mouth 0.34 cfu/cm2 Ryen et al., 2014
K (median Staph Dose Response from normal distribution)
8.21*10-8 cfu/cm2 Rose and Hass, 1999
Efficacy of Hand washing with soap 0.99 Luby, 2006
Assumed Safe Risk
Series11.0E-06
1.0E-05
1.0E-04Ri
sk o
f Inf
ectio
n (%
)
Risk due to Staph Exposure in Wounds
Series11.0E-06
1.0E-05
1.0E-04
1.0E-03
Considered Safe Limit
Wound Exposure
Risk
of I
nfec
tion
(%)
Risk due to Oral Ingestion
Series11.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
Considered Safe Limit
Oral ingestion Exposure
Risk
of I
nfec
tion
(%)
Risk Mitigation and Policy
• What is the impact of various occupational interventions on the risk of Staphylococcus aereus infection among rag pickers by skin, oral, and respiratory pathways? – Hand washing or hand sanitizer– Masks– Appropriate clothing barriers - footwear and
gloves• Which might be most effective?
Rag Picker Risk Framework
Microbial Concentration
(cfu/g)
Volume of waste per day
(g/day)
Total concentration in
waste/day (cfu/day)
Duration of 8-12 hours/day at site * 0.75 kg waste collected/hour * 5
Decay rate (e(-kt))
Infection
Infection
Dose-response (DR =
dose/person)
Dose ingested hand-to-mouth
in 5 minutes (DM)
Dose transferred object to skin in 5
minutes (DS)
Transfer efficiency object to skin (TEOS)
Frequency contact hand-to-mouth (ƒHM)
Transfer efficiency hands - mouth (TEHM)
Area of hand and arm contacting
waste (ACO)
= hand washing interventions = barrier interventions
Probability of wound (PW =
0.8)
Total area of hand/arm with
open wound (AWC)
frequency contact object and skin (ƒOS)
*set to 1 as constant
Risk due to Oral Ingestion After Washing the Exposed Body Parts
Series11.0E-06
1.0E-05
1.0E-04
1.0E-03
1.0E-02
1.0E-01
Considered Safe Limit
Oral ingestion Exposure
Oral ingestion Exposure after Hand Washing
Risk
of I
nfec
tion
(%)
Conclusions - Intervention Impact
• Hand washing with soap: typically 99% effective– Not likely to prevent infection of wound;
• Exposure of wound to contaminated fomite is immediate• Could reduce overall contamination on hands if practiced
frequently
– Not effective at preventing oral infection; cfu of Staphylococcus aereus deposited on hands is still >100,000cfu/wound
• Barriers like gloves (Not analyzed) – Act upstream of both exposure pathways by preventing hand
contamination– % effective
Risk Communication
• Rag pickers need to be informed of their occupational risk of exposure to high concentrations of hazardous pathogens.
• Waste sites are so contaminated by some organisms that follow-up hand washing may not be effective.
• Barriers, like the use of gloves (and masks) are far more likely to prevent skin contamination that can lead to bacterial entry into wounds and ingestion by mouth.
• Rag pickers need to be provided access to affordable and comfortable gloves, shoes, and clothing to protect themselves.
Acknowledgments
• Drexel team - Dr. Patrick Gurian• IITD team – Dr. Kumar• Mentors – Drs. Nema and Mittal