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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


(cfu/g)


(g/day)


waste/day (cfu/day)


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


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)


minutes (DS)



waste (ACO)


0.8)


open wound (AWC)



CFU/day * AWC * PW * ƒOS * TEOS = Ds (Dose through wound on skin)Where AWC = AW

ACO


(cfu/g)


(g/day)


Decay rate (e(-kt))

Gastrointestinal Exposure Dose via Hand-to-Mouth


waste/day (cfu/day)


in 5 minutes (DO)


minutes (DS)



waste (ACO)


0.8)


open wound (AWC)




(cfu/g)


(g/day)


Decay rate (e(-kt))



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


(cfu/g)


(g/day)


waste/day (cfu/day)


Decay rate (e(-kt))

Infection

Infection

Dose-response (DR =

dose/person)


in 5 minutes (DO)


minutes (DS)





waste (ACO)


0.8)


open wound (AWC)



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


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


(cfu/g)


(g/day)


waste/day (cfu/day)


Decay rate (e(-kt))

Infection

Infection

Dose-response (DR =

dose/person)


in 5 minutes (DM)


minutes (DS)





waste (ACO)

= hand washing interventions = barrier interventions


0.8)


open wound (AWC)



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


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

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