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SEMI S12-0298 © SEMI 1998 10 R2-1.3 The equa tions used in t his method to calculate th e oral and der mal “H ealth-Based Cleanup Levels (HBCL’s)” are: HBC L oral = RfD × B W SA O × MF × CE × AF O × EF HBCL dermal = RfD …

SEMI S12-0298 © SEMI 19989

RELATED INFORMATION 2

EXAMPLE OF METHOD FOR ESTABLISHING “NON-HAZARDOUS”

LEVELS

NOTE: This related information is not an official part of

SEMI S12 and is not intended to modify or supersede the

official standard. It has been derived from the work of the

originating task force. Publication was authorized by full

ballot procedures. Determination of the suitability of the

material is solely the responsibility of the user.

This method was compiled from various sources. The

applicability of this method and the validity of its

assumptions in the application for which it is

considered must be determined by an appropriate

professional.

R2-1 Method 1

This method is designed to be protective of the health

and safety of untrained and unprotected individuals. In

this method, “non-hazardous” level is determined by

assessment of the risk posed by potential exposure to

the contaminant(s). (This method is based on the

assumptions that 1) the exposed portions of a worker’s

body collect a single layer of the contaminant, with a

density half that of the layer on the contaminated

surface, in the course of a day and that 2) this

contaminant is then incorporated, at the end of the day,

into the body by either absorption or ingestion.) This

method is, therefore, probably inappropriate for

contaminants which are absorbed rapidly throughout

the day.

R2-1.1 Toxicity criteria are determined for each of the

chemicals identified as potentially leaving a residue. As

an example, toxicity criteria used are reference doses

(RfDs) for human uptake of chemicals (US EPA’s

Integrated Risk Information System, 1996), and no

significant risk levels (NSRLs) defined under

California’s Safe Drinking Water and Toxic

Enforcement Act of 1986 (Proposition 65). Daily

exposures to the RfD (expressed in mg/kg-day) over a

lifetime are not expected to cause adverse health effects

(non-cancer effects). Daily exposure to the NSRL

(µg/day) over a lifetime are considered to pose an

insignificant (less than 1 in 100,000) increased cancer

or reproductive risk.

R2-1.2 Oral and dermal exposures are considered.

Dermal exposure is assumed to occur through direct

contact with contaminated work surfaces (i.e., hands,

arms, and face). Oral exposure is assumed to occur

though direct contact with contaminated work surfaces

and hands, and subsequent contact between hand and

mouth.

SEMI S12-0298 © SEMI 1998 10

R2-1.3 The equations used in this method to calculate the oral and dermal “Health-Based Cleanup Levels

(HBCL’s)” are:

HBC

oral

= RfD × B

× MF × CE × AF

× EF

HBCL

dermal

= RfD × BW × ED

× CE × AF

× EF

Where :

RfD = EPA RfD [mg/kg − day]

BW = Body weight [70 kg]

ED = Exposure duration [0.5 days]

= Surface area of exposed hands [0.084 m

]

= Surface area of exposed hands, forearms, and head [0.316 m

]

MF = Fraction of exposed dermal are contacted by mouth [0.5/day]

CE = Skin contact efficiency [0.5]

= Gastro - intestinal absorption factor [1.0] (conservative)

= Dermal absorption factor [0.01]

EF = Exposure factor [12 hours/24 hours; 250 days/365 days; 40 years/70 years = 0.20]

Body weight and surface area factors are as suggested by EPA’s Exposure Factors Handbook (1989). The fraction

of skin contaminant that will be ingested orally (MF) is conservatively assumed to be 50%. This is approximately

equivalent to a person ingesting all of the chemical that contacts the palms of the hands, but not the backs. Contact

efficiency (CE) refers to the fraction of chemical that is removed from the contaminated surface through contact

with the skin. It is assumed that no more than 50% of the chemical contamination from equipment will rub off the

surface and adhere to the skin. Oral and dermal absorption factors are chosen as the most conservative numbers due

to limited available data.

The exposure factor (EF) represents the fraction of time that a person could be expected to be in contact with

chemical contamination from exposed surfaces. Exposure to surfaces is assumed to follow an occupational exposure

scenario. This scenario includes the following conservative assumptions:

• A person works at the facility for 40 years of a 70-year lifetime;

• Exposure occurs 250 days per year (365 days);

• The skin is in contact with the chemicals for 12 hours per day. This assumes that the chemicals are not removed

from the skin until washed, and the skin is washed only once per day.

R2-1.4 The final HBCL for each chemical is then the lower of the levels for oral or dermal exposure routes.

NOTE: These HBCLs represent levels that are considered to be health-protective for a person who contacts equipment with

residual contamination on a daily basis. These values are based on extremely conservative assumptions and are likely to provide

an overestimate of a health-protective clean-up level.

NOTICE: These standards do not purport to address

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appropriate safety and health practices and determine

the applicability of regulatory limitations prior to use.

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other relevant literature respecting any materials

mentioned herein. These standards are subject to

change without notice.

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