T he N ational Institute for O ccupational Safety and H ealth (NIOSH) recommends that em ployee exposure to acrylonitrile in the workplace be controlled so that no worker will be exposed to acrylonitrile in excess of 4 ppm (8.7 mg/cu m) in air as determ ined by a 4-hour sample collected at 0 2 liter/m inute Because it is not possible at present to establish a safe exposure level for a carcinogen, the NIOSH recom m enda tion is to restrict exposure to very low levels that can still be reliably measured in the workplace. The recommended exposure limit of 4 ppm is the lowest level at which a reliable estimate of oc cupational exposure to acrylonitrile can be deter m ined at this time because of a lim itation in the air m easurement technique Short-term studies are presently underway within the Institute to resolve those problems causing the limitation. If the studies bear positive results, the Institute will forward a recom m endation to reduce the permissable exposure limit to some value less than 4 ppm. The present Federal Standard is 20 ppm , determ ined as a time-weighted average (TWA) concentration for up to an 8-hour work shift in a 40-hour workweek. In addition, the standard contains recom m endations for m edical sur veillance, inform ing em ployees of hazards, sanitation, work practices, labeling and posting, personal protective clothing and equipm ent, m onitoring, and recordkeeping.
The recommended standard is designed to protect the health and provide for the safety of employees for up to a 10-hour work shift, 40hour workweek, over a working lifetime. Com pliance with all sections of the standard should, at the m inim um , substantially reduce the risk of acrylonitrile-induced cancer and prevent other adverse effects of exposure to acrylonitrile in the workplace. The employer should regard the recommended workplace environm ental lim it as the upper boundary for exposure and make every effort to keep the exposure as low as possible
The acute toxic effects of acrylonitrile are similar to those from cyanide poisoning. Toxic effects of acrylonitrile inhalation which have been noted in animals include damage to the central nervous system, lungs, liver, and kidneys. Embryotoxic effects in mice have also been re ported. However, the more recent evidence of acrylom tnles chronic toxicity has caused a reassessm ent of the hazard o f w orkers of acrylonitrile In April 1977, the M anufacturing Chemists Association reported interim results of two-year feeding and inhalation studies (con ducted by the Dow Chemical Company) of acrylonitrile in laboratory rats. By both routes of adm inistration, acrylonitrile caused the develop m ent of central nervous system tum ors and Zymbal gland carcinomas; no such tum ors were seen in control animals. Exposure to 80 ppm of acrylonitrile also revealed an increased incidence of mammary region masses.
A prelim inary epidem iologic study con ducted by the E.I D uPont de N em ours & Com pany, Inc of a cohort of 470 acrylonitrile polymerization workers from the com pany's Camden, South Carolina, textile fibers plant indi cates an excess risk of lung and colon cancer among workers w ith potential acrylonitrile ex posure. A total of 16 cancer cases occurred by be tween 1969 and 1975 among the cohort first ex posed between 1950 and 1955; only 5.8 cancer cases would have been expected, based on D u Pont Company rates (excluding the cohort). A lth o u g h th e ep id em io lo g ic fin d in g s are preliminary in nature and may not alone provide definitive evidence of the carcinogenicity of acrylonitrile in man, when considered in light of the laboratory experim ents dem onstrating car cinogenicity in rats, a serious suspicion is raised that acrylonitrile is a hum an carcinogen Thus, N IO SH believes th at acrylonitrile m ust be handled in the workplace as a suspect hum an car cinogen.
Acrylonitrile is an explosive, flammable liq uid having a normal boiling point of 77 C and a vapor pressure of 80 mm H g (20 C). Synonyms for acrylonitrile include acrylon, carbacryl, cyanoethylene, fum igrain, 2-propenem trile, VCN, ventox, and vinyl cyanide.
A p p ro x im ately 1.5 b illio n p o u n d s o f acrylonitrile are m anufactured each year in the U nited States by the reaction of propylene w ith ammonia and oxygen in the presence of a catalyst The major use of acrylonitrile is in the production of acrylic and modacrylic fibers by copolymerization with m ethyl acrylate, m ethyl m ethacrylate, vinyl acetate, vinyl chloride, or vinylidene chloride. Acrylic fibers are used in the m anufacture of apparel, carpeting, blankets, draperies, and upholstery Some applications of modacrylic fibers are synthetic furs and hair wigs.
O ther major uses of acrylonitrile include the m anufacture of acrylom trile-butadiene-styrene (ABS) and styrene-acrylomtrile (SAN) resins (used to produce a variety of plastic products), nitrile elastomers and latexes, and other chem i cals, such as ad ip o m tn le and acrylam ide. Acrylonitrile is also used as a fumigant. NIOSH estimates that approximately 125,(XX) persons are potentially exposed to acrylonitrile in the workplace.
The recom m ended standard is part of a con tinuing series of recommendations developed by NIOSH in accordance w ith the Occupational Safety and H ealth Act of 1970. The recom m ended standard is being transm itted to the D epartm ent of Labor September 29, 1977, for review and consideration in the standard setting process. If research by N IO SH results in the developm ent of im proved m ethods for sampling and analysis of acrylonitrile in air from the oc cupational environm ent, inform ation regarding the new m ethods will be forwarded to the D epartm ent of Labor.

# I. RECOM M ENDATIONS FOR A N ACRYLONITRILE STANDARD
The N ational Institute for O ccupational Safety an d H e a lth (N IO S H ) re c o m m e n d s th a t employee exposure to acrylonitrile in the w ork place be controlled by adherence to the following sections. The standard is designed to protect the health and provide for the safety of employees for up to a 10-hour work shift, 40-hour workweek, over a working lifetime. Compliance w ith all sec tions of the standard should, at the m inim um , substantially reduce the risk of acrylonitrile-induced cancer and prevent other adverse effects of exposure to acrylonitrile in the workplace The employer should regard the recom m ended w ork place environm ental lim it as the upper boundary for exposure and make every effprt to keep the exposure as low as possible The criteria and stan dard will be subject to review and revision as necessary.
Acrylonitrile is an explosive, flammable liquid having a normal boiling point of 77 C and a vapor pressure of 80 mm Hg (20 C) Synonyms for a c ry lo n itrile in c lu d e a c ry lo n , c a rb a c ry l, cyanoethylene, fum igrain, 2-propenenitrile, VCN, ventox, and vinyl cyanide.
A p p ro x im a te ly 1.5 b illio n p o u n d s o f acrylonitrile are m anufactured each year in the U nited States by the reaction of propylene with ammonia and oxygen in the presence of a catalyst. The major use of acrylonitrile is in the production of acrylic and modacrylic fibers by copolymerization with m ethyl acrylate, m ethyl methacrylate, vinyl acetate, vinyl chloride, or vinylidene chloride. Acrylic fibers are used in the manufacture of apparel, carpeting, blankets, draperies, and upholstery Some applications of modacrylic fibers are synthetic furs and hair wigs. O ther major uses of acrylonitrile include the m anufacture of acrylonitrile-butadiene-styrene (ABS) and styrene-acrylonitrile (SAN) resins (used to produce a variety of plastic products), nitnle elastomers and latexes, and other chem i cals, such as adiponitrile and acrylam ide Acrylonitrile is also used as a fumigant.
NIOSH estimates that approximately 125,000 persons are potentially exposed to acrylonitrile in the workplace.
The acute toxic effects o f acrylonitrile are sim i lar to those from cyanide poisoning Toxic effects of acrylonitrile inhalation which have been noted in animals include damage to the central nervous system, lungs, liver, and kidneys. Embryotoxic effects in mice have also been reported. However, the more recent evidence of acrylonitriles chronic toxicity has caused a reassessment of the hazard to workers of acrylonitrile In April 1977, the M anufacturing Chemists Association reported interim results of two-year feeding and inhala tion studies (conducted by the Dow Chemical Company) of acrylonitrile in laboratory rats. By both routes of adm inistration, acrylonitrile caused the developm ent of central nervous system tum ors and Zymbal gland carcinomas; no such tumors were seen in control animals. Ex posure to 80 ppm of acrylonitrile also revealed an increased incidence of mammary region masses A preliminary epidemiologic study conducted by the E I D uPont de N em ours & Company, Inc of a cohort of 470 acrylonitrile polymerization workers from the com pany's Camden, South Carolina, textile fibers plant indicates an excess risk of lung and colon cancer among workers with potential acrylonitrile exposure A total of 16 cancer cases occurred between 1969 and 1975 among the cohort first exposed between 1950 and 1955, only 5 8 cancer cases would have been ex pected, based on D uPont Company rates (ex cluding the cohort) A lthough the epidemiologic findings are preliminary in nature and may not alone provide definitive evidence of the car cinogenicity of acrylonitrile in man, when con sidered in light of the laboratory experiments dem onstrating carcinogenicity in rats, a serious suspicion is raised that ac.ylom trile is a human carcinogen Thus, NIOSH believes that acrylonitrile must be handled in the workplace as a suspect hum an carcinogen "Occupational exposure to acrylonitrile" refers to any workplace situation in which acrylonitrile is m anufactured, polymerized, used, handled, or stored. All sections of the standard shall apply w here th e re is o ccu p atio n al exp osu re to acrylonitrile.

# Section 1 -Environmental (Workplace Air)
(a) Concentration A crylonitrile shall be controlled in the workplace so that the concentration of airborne acrylonitrile, sampled and analyzed according to the procedures in Appendix I, is not greater than 4 pf>m (approximately 8 7 mg/cu rr) of breathing zone air (b) Sampling and Analytical Methods The environm ental lim it represents the lowest reliably detectable concentration of acrylonitrile measurable by the recommended sampling and analytical m ethods Procedures for the collection and analysis of acrylonitrile in air shall be as pro vided in Appendix I or by any methods shown to be equivalent in accuracy, precision, and sen sitivity to the methods specified.

# Section 2 -Medical
Medical surveillance shall be m ade available as specified below for all workers occupationally ex posed to acrylonitrile.
(a) Preplacem ent initial, and annual medical examinations shall include:
(1) An initial or interim medical and work history with special attention to skin, respiratory and gastrointestinal systems, and those non specific symptoms, such as headache, nausea, vomiting, dizziness, weakness, or other central nervous system dysfunctions that may be associ ated w ith chronic exposure.
(2) A physical examination giving particu lar attention to the skin, thyroid, respiratory system, and central nervous system.
(3) A 14" x 17" posteroanterior chest Xray.
(4) Further tests of the intestinal tract, such as proctosigmoidoscopy, on all workers over the age of 40 and all other workers who, in the opin ion of the responsible physician, show appropri ate indications.
(5) A judgm ent of the worker's ability to use positive pressure respirators.
(b) Initial medical examinations shall be made available to presently employed workers as soon as possible after the prom ulgation of a standard based on these recommendations.
(c) The employer shall ensure that employees trained in first-aid m easures are on duty whenever there is occupational exposure to acrylonitrile.
(d) Two physician's-treatm ent kits shall be immediately available to trained medical person nel at each plant where there is a potential for the release of, or for contact with, acrylonitrile. These kits should contain, as a minimum:
1. Two (2) boxes (2 dozen) ampules; each am pule containing 0.3 ml of amyl nitrite. Ampules shall be replaced biannually or sooner if needed to ensure their potency.
2. Two (2) ampules of sterile sodium nitrite solution (10 ml of a 3% solution in each).
3. Two (2) ampules of sterile sodium thiosulfate solution (50 m l of a 25% solution in each).
4. 2 sterile 10-ml syringes with intravenous needles.
5. 1 sterile 50-ml syringe w ith intravenous needle.
6. 1 tourniquet.
7. 1 gastric tube (rubber). 8 1 non-sterile 100-ml syringe. One kit should be portable in order that it may be carried by medical personnel while accompany ing a patient to the hospital. The other kit should be kept under lock and key to assure that it is in tact and available when and if needed. The key should be readily available at all times to the work supervisor on duty and the storage place should be of such construction as to allow access in the event of loss of the key.
(e) First-aid kits shall be immediately availa ble at workplaces where there is a potential for th e release, a c c id e n ta l or o th erw ise, o f acrylonitrile. This kit shall contain as a m inim um two (2) boxes Qf ampules (2 dozen), each contain ing 0-3 m l of amyl nitrite. Ampules shall be replaced biannually or sooner if needed to ensure their potency. The amyl nitrite ampules should be protected from high temperatures. In all cases, the contents of the physician's-treatm ent and first-aid kits shall be replaced before the m anufacturer's assigned expiration dates.
(f) Appropriate medical services shall be made available to any employee with adverse health effects from acrylonitrile in the workplace.
(g) Medical records shall be m aintained for all workers occupationally exposed to acrylonitrile. Pertinent medical records shall be m aintained for 30 years following the last occupational exposure to acrylonitrile. These records shall be m ade available to the designated medical representa tives of the Secretary of Health, Education, and Welfare, of the Secretary of Labor, of the em ployer, and of th e em ployee or form er employee.

# Section 3 -Labeling and Posting
A label shall be placed on each shipping and storage container of acrylonitrile and all areas w h ere th e re is o c cu p atio n al exp osu re to acrylonitrile shall be posted.
All warning signs shall be printed both in English and in the predom inant language of non-English-reading workers Illiterate workers and workers reading languages other than those used on labels and posted signs shall receive verbally disseminated inform ation regarding hazardous areas and shall be inform ed of the instructions printed on labels and signs.
(a) Labeling If respiratory protection is required in accor dance with Section 4, the following statem ent in large letters shall be added to the required sign:

# Section 4 - Personal Protective Clothing and Equipment
(a) Protective Clothing
(1) Employers shall provide and ensure that employees use gloves, face shields (eightinch m inim um ) and other appropriate protective clothing or equipm ent necessary to prevent skin contact w ith liquid acrylonitrile. Face shields shall comply w ith 29 CFR 1910.133 (a)(2), (a)(4),  (a)(5), and (a)(6).
(2) W here exposure of an employee's body to liquid acrylonitrile may occur, employers shall provide facilities for quick drenching of the body within the im m ediate work area for emergency use. (3) Employers shall ensure that any per vious clothing which becomes wet with, or im pervious clothing which becomes grossly con tam inated with, acrylonitrile is removed im mediately and not reworn until the acrylonitrile has been removed from the clothing.
(4) Employers shall ensure that clothing wet with liquid acrylonitrile is placed in closed containers for storage until it can be discarded or until acrylonitrile is removed from the clothing. If the clothing is to be laundered or otherwise cleaned to remove the acrylonitrile, the employer shall inform the person (s) perform ing the opera tion of the hazardous properties of acrylonitrile Work clothing shall not be taken home by employees.
(5) Eye protection shall be provided by the employer and used by the employees where eye contact with liquid acrylonitrile is likely. Selec tion, use, and maintenance of eye protective equipm ent shall be in accordance with the provi sions of the American N ational Standard Practice for Occupational and Educational Eye and Face Protection, ANSI Z87 1-1968. Unless eye protec tion is afforded by a respirator hood or facepiece, protective goggles  or a face shield shall be worn at operations where there is danger of contact of the eyes with liquid acrylonitrile because of spills or splashes. If there is danger of liquid acrylonitrile striking the eyes from underneath, or around the sides of the face shield, safety goggles shall be worn as added protection.
(6) The employer shall ensure that all per sonal protective devices are inspected regularly and m aintained in clean and satisfactory working condition (b) Respiratory Protection (1) Engineering controls shall be used when feasible to keep concentrations of airborne acrylomtrile at or below the recommended en vironmental limit Respiratory protective equip m ent may only be used in the following circum stances (A) During the tim e necessary to install or test the required engineering controls (B) For operations such as nonroutine maintenance and repair activities in which brief exposure at concentrations in excess of the recommended environm ental limit may occur (C) During emergencies when con centrations of airborne acrylomtrile m ight exceed the recommended environmental limit
(2) When a respirator is perm itted by paragraph (b)(1) of this section, it shall be selected and used in accordance with the follow ing requirements (A) The employer shall establish and enforce a respiratory protective program. The re quirements for such a program are listed in 29 CFR 1910 H 4 (B) The employer shall provide respira tors in accordance with Table 1-1 and shall ensure that employees use the respirators in a proper manner when the concentration of airborne acrylomtrile exceeds the recommended environ mental limit The respirators shall be those ap proved by NIOSH or the M ining Enforcement and Safety Administration The standard for ap proval is specified in 30 CFR 11 The employer shall ensure that respirators are properly cleaned, m aintained, and stored when not in use

# Section 5 -Informing Employees of Hazards from Acrylonitrile
(a) The em ployer shall ensure th at each employee assigned to work in an area where there is occupational exposure to acrylomtrile is in formed of the hazards and relevant symptoms of exposure to acrylonitrile, and of proper condi tions and precautions for the handling and use of acrylonitrile Workers shall be advised that skin exposure to liquid acrylonitrile may cause blister form ation and burns and that exposure to air borne acrylonitrile may have an im m ediate effect of causing unconsciousness or respiratory failure and, on a long-term basis, may increase the risk of developing cancer, particularly of the lungs and large intestine. Inform ation shall be given to employees at the beginning of em ploym ent and at least twice a year thereafter.
(b) The employer shall institute a continuing education program , conducted by instructors qualified by experience or training, to ensure that all employees have current knowledge of job hazards, p ro p e r m ain ten an ce and clean u p methods, and proper respirator use The instruc tional program shall include a description of the environm ental and medical surveillance pro cedures and of the advantages to the employee of participating in these procedures. Instruction shall include the inform ation specified in the "M aterial Safety Data Sheet," which shall be kept on file and readily accessible to employees at all places of em ploym ent where there is occupa tional exposure to acrylomtrile Workers engaged in maintenance and repair shall be included in these training programs (c) Required inform ation shall be recorded on the "Material Safety Data Sheet" or on a similar form approved by the Occupational Safety and H ealth A dm inistration, US D ep artm ent of Labor.

# Section 6 -Work Practices
(a) Control of Airborne Acrylonitrile Engineering controls, such as process enclosure or local exhaust ventilation, shall be used to keep concentrations of airborne acrylonitrile at or below the recom m ended environm ental limit. If Greater than 2 mg/cu m or E m ergency (entry into area of unknown c o n c e n t r a t i o n f o r emergency purposes)
(1) Self-contained breathing apparatus w ith full facepiece operated in pressure-demand or other positive pressure mode
(2) Combination Type C supplied-air respirator with full facepiece operated in pressure-dem and mode and auxiliary self-contained air supply used, ventilation systems shall be so designed and operated as to prevent accumulation or recircula tion of airborne acrylonitrile in the workplace en vironm ent and to effectively remove acrylonitrile from the breathing zone of employees. Exhaust ventilation systems discharging to outside air must conform to applicable local, state, and federal regulations and m ust not constitute hazards to employees or to the general popula tion Before m aintenance work on control equip m ent begins, sources of airborne acrylonitrile shall be elim inated to the extent feasible Enclosures, exhaust hoods, and ductw ork shall be kept in good repair so that design airflows are maintained. Airflow at each hood shall be measured at least semiannually and preferably m onthly. C ontinuous airflow indicators are recom m ended, such as water or oil m anometers properly m ounted at the juncture of fume hood and duct throat (marked to indicate acceptable airflow). A log shall be kept showing design airflow and results of semiannual or m onthly in spections.
W h enev er feasible, o p e ra tio n s in v o lv in g acrylonitrile should be placed in an isolated area, in com bination with other engineering controls, to reduce exposure of employees not directly concerned with the acrylonitrile operations.
(b) Regulated Areas Regulated areas shall be established and m ain tained where there is occupational exposure to acrylonitrile, and access to these areas shall be lim ited to authorized persons who have been properly inform ed of the potential hazards of acrylonitrile and proper control measures. A daily roster shall be made o f ail persons who enter regulated areas.
( (5) Where a fan is located in ductwork and where acrylonitrile is present in the ductw ork in concentrations greater than 7,500 ppm (approx imately 25 percent of the lower flammable limit), the rotating element of the fan shall be of nonsparking material or the casing shall consist of, or be lined with, nonsparking material There shall be sufficient clearance between the rotating ele m ent of the fan and the fan casing to prevent contact between the rotating element and the casing (6) Sources of ignition, such as smoking or open flames, are prohibited where acrylonitrile presents a fire or explosion hazard (f) Disposal of Waste Waste material shall be disposed of in a m anner that is not hazardous to employees or to the general population Spills of acrylonitrile and flushing of such spills shall be channeled for ap propriate treatm ent or collection for disposal. They shall not be channeled directly into the sanitary sewer system. Acrylonitrile wastes shall be appropriately m arked and any operations g e n e ra tin g airb o rn e a c ry lo n itrile shall be enclosed. In selecting the m ethod of waste dis posal, applicable local, state, and federal regula tions should be consulted (g) Storage Containers of acrylonitrile shall be kept tightly closed when not in use. Containers shall be stored in a safe m anner to minimize the possibility of ac cidental breakage or spills.
(h) General Work Practices (1) G ood housekeeping practices shall be observed to prevent contam ination of areas and equipm ent with liquid acrylonitrile and to pre vent buildup of such contam ination
(2) G ood personal hygiene practices should be encouraged Employees shall be re quired to wash all exposed areas of the body upon exiting from regulated areas Employees occupa tionally exposed to acrylonitrile shall be required to shower at the end of the workshift (i) W ork Clothing/Protective Clothing (1) Coveralls or similar full-body protective clothing and head, leg, and shoe coverings shall be worn by each employee entering a regulated area Upon exiting from a regulated area, the pro tective clothing shall be left at the point of exit W ith the last exit of the day, the protective clothing shall be placed in a suitably marked and closed container for disposal or laundering
(2) Such clothing shall be changed as soon as possible if accidentally contam inated with liq uid acrylonitrile
(3) The employer shall provide for the laundering of this clothing and shall ensure that soiled work clothing is not taken home by the employee. Precautions shall be taken to protect personnel who handle and launder soiled clothing. These workers shall be advised of the hazards of and means of preventing exposure to acrylonitrile Section 7 -Sanitation (a) Em ergency show ers and eye-flushing fountains with adequate pressure of cool water shall be provided and be quickly accessible in areas where there is potential of skin or eye con tact with acrylonitrile. This equipm ent shall be frequently inspected and m aintained in good working condition.
(b) Locker-room facilities, including showers and washbasins, located in nonexposure areas, shall be provided for employees required to change clothes before and after each work shift. The facilities shall provide for storage o f street clothing and clean work clothing separately from soiled work clothing Covered containers shall be provided for work clothing removed at the end of the work shift or after a contam ination inci dent The clothing shall be held in these con tainers until it is removed for decontam ination or disposal (c) Food preparation, dispensing (including vending m ach in es), and e atin g shall be prohibited in areas where there is occupational exposure to acrylonitrile Eating facilities pro vided for employees shall be located in nonex posure areas Washing facilities should be accessi ble nearby.
(d) Smoking and carrying smoking or chewing materials shall be prohibited in work areas where there is occupational exposure to acrylonitrile.

# Section 8 -Monitoring and Recordkeeping Requirements (a) M onitoring
(1) As soon as possible after prom ulgation of a standard based on these recommendations, each employer who has a place of em ploym ent in w h ic h a c r y lo n i tr i le is m a n u f a c tu r e d , polymerized, handled, stored, or otherwise used shall determ ine by an industrial hygiene survey the extent of exposure to acrylonitrile Surveys shall be repeated at least once every year and within 30 days of any process change likely to result in occupational exposure to acrylonitrile Records of these surveys, including the basis for any conclusion that there is no occupational ex posure to acrylonitrile, shall be retained until the next survey has been completed.
(2) If there is occupational exposure to acrylonitrile a program of personal m onitoring shall be instituted to measure or perm it calcula tion of the exposure of all employees.
(A) In all personal m onitoring, samples representative of the breathing zones of the employees shall be collected.
(B) For each environm ental determ ina tion, a sufficient num ber of samples shall be taken to characterize the employees' exposures during each work shift. Variations in work and production schedules and in employees' locations and job functions shall be considered in choosing sampling times, locations, and frequencies.
(C) Each operation in each work area shall be sam pled at least once every 3 months.
(3) If an employee is found to be exposed to acrylonitrile in excess of the recom m ended en vironm ental lim it, the exposure of th at employee shall be measured at least once a week, control measures shall be initiated, and the employee shall be notified of the extent of the exposure and of the control measures being im plem ented. Such m onitoring shall continue until tw o consecutive determ inations, 1 week apart, indicate that the em ployee's exposure no longer exceeds the recom m ended environm ental lim it. R outine m onitoring may then be resumed.
(b) Recordkeeping Environm ental m onitoring records shall be m aintained for at least 30 years after the em p lo y ee's last o c cu p atio n al exposure to acrylonitrile. These records shall include the dates and times of measurements, job function and location of employees within the worksite, m ethods of sampling and analysis used, types of respiratory protection in use at the tim e of sam pling, environm ental concentrations found, and identification o f exposed em ployees. Each employee shall be able to obtain inform ation on that employee's own environm ental exposures. Daily rosters of authorized persons who enter regulated areas shall be retained for 30 years. En vironm ental m onitoring records and entry rosters shall be made available to designated representa tives of the Secretary of Labor and of the Secre tary of Health, Education, and Welfare.
Pertinent medical records for each employee shall be retained for 30 years after the employee's last occupational exposure to acrylonitrile Records of environm ental exposures applicable to an employee should be included in that em ployee's m edical records. These m edical records shall be m ade available to the designated medical representatives of the Secretary of Labor, of the Secretary of Health, Education, and Welfare, of the employer, and of the employee or former employee (c) Employee Observation of M easurement (1) The em ployer shall give affected employees or their representatives an oppor tunity to observe any measurement made p u r suant to the standard of employee exposure to acrylomtrile.
(2) W hen observation of m easurement of employee exposure to acrylonitrile requires entry into an area where the use of personal protective devices, including respirators, is required, the ob server shall be provided with and required to use such equipm ent and comply with all other ap plicable safety procedures.
(3) W ithout interfering with the measure m ent, observers shall be entitled to.
(i) Receive an explanation of the m easurement procedure.
(li) Observe all steps related to the m easurement of the concentration of airborne acrylonitrile that are being perform ed at the place of exposure; and
(iii) Record the results obtained.

# APPENUIX I PREFACE TO NIOSH METHOD N O . SI 56 (ACRYLONITRILE)
NIOSH M ethod N o SI 56 (copy attached), with slight modifications, is recommended for sampling and analysis of acrylonitrile in air M ethod SI 56 utilizes a charcoal tube for collec tion o f the sam ple and analysis by gaschromatography.
Data from the Standards Completion Program (SCP) indicates that at lower loadings than about 400 micrograms on the charcoal tube, the desorp tion efficiency may not be adequate, thus, the analysis would be questionable.
In addition, since the breakthrough studies of the SCP were not carried out beyond 48 liters {0.2 liter/m inu te for 4 hours at 92.0 mg acrylonitrile/cu m (42.4 ppm )] and since the effects o f h u m id ity on b re a k th ro u g h are unknow n, it cannot be presently assumed that sampling for 8 hours can be accomplished w ith out breakthrough Therefore, based upon the best available data, the Institute has determ ined that 4 ppm of acrylonitrile is the lowest concentration measura ble at the present tim e by a reliable sam pling/analytical m ethod To determ ine the workplace air concentration of acrylonitrile, collect a 4-hour sample at a flow rate of 0 2 liter/m inute. 1.2 The charcoal in the tube is transferred to a small, stoppered sample container, and the analyte is desorbed with methanole.
1 3 An aliquot of the desorbed sample is injected into a gas chromatograph 1 4 The area of the resulting peak is deter m ined and compared with areas obtained for standards 2 Range and Sensitivity 2 1 This m ethod was validated over the range of 17 5-70.0 mg/cu m at an atmospheric tem perature and pressure of 22C and 760 mm Hg, using a 20-liter sample. U nder the conditionsof sample size (20 liters) the probable useful range of this m ethod is 4.5-135 mg/cu m The m ethod is capable of measuring m uch smaller amounts if the desorption efficiency is adequate Desorption efficiency m ust be determ ined over the range used.
2 2 The upper limit of the range of the m ethod is dependent on the adsorptive capacity of the charcoal tube This capacity varies w ith the concentrations of acrylonitrile and other subs tances m the air. The first section of the charcoal tube was found to hold at least 3 97 mg of acrylonitrile when a test atmosphere containing 92.0 mg/cu m of acrylonitrile in air was sampled at 0.18 liter per m inute for 240 m inutes, at that time the concentration of acrylonitrile in the effluent was less than 5% of that in the influent (The charcoal tube consists of two sections of ac tivated charcoal separated by a section of urethane foam. See Section 6.2) If a particular at mosphere is suspected of containing a large am ount of contam inant, a smaller sampling volume should be taken.

# Interferences
3 1 W hen the am ount of water in the air is so great that condensation actually occurs in the tube, organic vapors will not be trapped effi ciently. Preliminary experiments using toluene indicate that high hum idity severely decreases the breakthrough volume 3.2 W hen in te rfe rin g co m p o u n d s are known or suspected to be present in the air, such inform ation, including their suspected identities, should be transm itted with the sample 3 3 It m ust be emphasized that any com pound which has the same retention tim e as the analyte at the operating conditions described in this m ethod is an interference Retention time data on a single column cannot be considered proof of chemical identity 3 4 If the possibility of interference exists, separation conditions (column packing, tem perature, etc.) m ust be changed to circum vent the problem 4. Precision and Accuracy 4.1 The Coefficient of Variation (CV-p) for the total analytical and sampling m ethod in the range of 17.5-70.0 mg/cu m was 0 073. This value corresponds to a 3.3 mg/cu m standard deviation at the OSHA standard level. Statistical inform a tion and details of the validation and experim en tal test procedures can be found in Reference 11.2 4.2 On the average the concentrations ob tained at the OSHA standard level using the overall sampling and analytical m ethod were 6.0% lower than the "true" concentrations for a limited num ber of laboratory experiments Any difference between the "found" and "true" con centrations may not represent a bias in the sam pling and analytical m ethod, but rather a random - variation from the experimentally determ ined # "true" concentration Therefore, no recovery cor rection should be applied to the final result in Section 10 5 5 A dvantages and D isadvantages o f the M ethod 5 1 The sampling device is small, portable, and involves no liquids Interferences are minimal, and most of those which do occur can be eliminated by altering chrom atographic con ditions The tubes are analyzed by means of a quick, instrum ental m ethod The m ethod can also be used for the simultaneous analysis of two or more substances suspected to be present in the sam e s a m p le by s im p ly c h a n g in g g as chrom atographic conditions 5 2 One disadvantage of the m ethod is that the am ount of sample which can be taken is limited by the num ber of milligrams that the tube will hold before overloading. W hen the sam ple value obtained for the backup section of the charcoal tube exceeds 259? of that found on the front section, the possibility of sample loss exists 5 3 Furtherm ore, the precision o f the m ethod is lim ited by the reproducibility of the pressure drop across the tubes This drop will affect the flow rate and cause the volume to be imprecise, because the pum p is usually calibrated for one tube only 6 Apparatus 6.1
A calibrated personal sampling pum p whose flow can be determ ined within  5% at the recom m ended flow rate. (Reference 11.3) 6 2 Charcoal tubes: glass tube with both ends flame sealed, 7 cm long with a 6-mm O D and a 4-mm I D , containing 2 sections of 20/40 mesh activated charcoal separated by a 2-mm portion of urethane foam. The activated charcoal is prepared from coconut shells and is fired at 600C prior to packing The adsorbing section contains 100 mg of charcoal, the backup section 50 mg A 3-mm portion of urethane foam is placed between the outlet end of the tube and the backup section A plug of silylated glass wool is placed in front of the adsorbing section The pressure drop across the tube m ust be less than one inch of m ercury at a flow rate of 1 liter per m inut" c 3 Gas chrom atograph equipped w ith a flame ionization detector 6 4 Colum n (4-ft x 1/4-in stainless steel) packed with 50/80 mesh Porapak, Type Q 6 5 An electronic integrator or some other suitable m ethod for measuring peak areas 6 6 Two-m illiliter sample containers with f glass stoppers or Teflon-lined caps. If an auto m atic sample injector is used, the associated vials may be used. 6 7 M icrohter syringes 10-microliter, and other convenient sizes for m aking standards 6.8 Pipets-1 O-ml delivery pipets. 6 9 Volumetric flasks 10-ml or convenient sizes for m aking standard solutions 7 Reagents 7 1 Chromatographic quality methanol. 7 2 Acrylonitrile, reagent grade.   8.3.6 The tem perature and pressure of the atm osphere being sam pled should be recorded If pressure reading is not available, record the elevation.
The charcoal tubes should be cap ped w ith the supplied plastic caps immediately after sampling. U nder no circumstances should rubber caps be used. 8.3.8 W ith each batch of ten samples subm it one tube from the same lot of tubes which was used for sample collection and which is sub jected to exactly the same handling as the sam ples except that no air is drawn through it. Label this as a blank. 8 3.9 Capped tubes should be packed tightly and padded before they are shipped to minimize tube breakage during shipping 8 3 10 A sample of the bulk material should be subm itted to the laboratory in a glass container with a Teflon-lined cap This sample should not be transported in the same container as the charcoal tubes. 6. 155C colum n tem perature 8.4.4 Injection. The first step in the analysis is the injection of the sample into the gas chromatograph. To eliminate difficulties arising from blow back or distillation within the syringe needle, one should employ the solvent flush in jection technique. The 10-microliter syringe is first flushed w ith solvent several times to wet the barrel and plunger Three microliters of solvent are drawn into the syringe to increase the ac curacy and reproducibility of the injected sample volume. The needle is removed from the solvent, and the plunger is pulled back about 0.2 microliter to separate the solvent flush from the sample with a pocket of air to be used as a marker The needle is then immersed m the sam ple, and a 5-microliter aliquot is withdrawn, tak ing into consideration the volume of the needle, since the sample in the needle will be completely injected After the needle is removed from the sample and prior to injection, the plunger is pulled back 1.2 microliters to minimize evapora tion of the sample from the tip of the needle. O b serve that the sample occupies 4 9-5 0 microliters in the barrel of the syringe. Duplicate injections of each sample and standard should be made. N o more than a 3A difference in area is to be ex pected An autom atic sample injector can be used if it is shown to give reproducibility at least as good as the solvent flush m ethod 8.4.5 Measurement of area. The area of the sample peak is measured by an electronic in tegrator or some other suitable form of area measurement, and preliminary results are read from a standard curve prepared as discussed below 8 5 Determ ination of Desorption Efficien cy 8.5 1 Importance of determ ination The desorption efficiency of a particular com pound can vary from one laboratory to another and also from one batch of charcoal to another. Thus, it is necessary to determ ine at least once the percen tage of the specific com pound that is removed in the desorption process, provided the same batch of charcoal is used. 8 5.2 P ro c e d u re fo r d e te rm in in g d eso rp tio n efficiency . A c tiv a te d charcoal equivalent to the am ount in the first section of the sampling tube (100 mg) is measured into a 2.5 in, 4-m m I D glass tube, flame sealed at one end. This charcoal m ust be from the same batch as that used in obtaining the samples and can be ob tained from unused charcoal tubes. The open end is capped with Parafilm. A known am ount of hexane solution of acrylonitrile containing 0.239 g/m l is injected directly into the activated char coal with a m icroliter syringe, and the tube is capped w ith more Parafilm. W hen using an auto matic sample injector, the sample injector vials, capped with Teflon-faced septa, may be used in place of the glass tubes.
The am ount injected is equivalent to that present in a 20-liter air sample at the selected level. Six tubes at each of three levels (0 5X, IX , and 2X of the standard) are prepared in this m an ner and allowed to stand for at least overnight to assure com plete adsorption of the analyte onto the charcoal. These tubes are referred to as the samples. A parallel blank tube should be treated in the same m anner except that no sample is ad ded to it. The sample and blank tubes are desorbed and analyzed in exactly the same m an ner as the sampling tube described in Section 8.4.
Two or three standards are prepared by injecting the same volume of com pound into 1.0 ml of m ethanol with the same syringe used in the preparation o f the sam ples. These are analyzed with the samples.
The desorption efficiency (D.E.) equals the average weight in mg recovered from the tube divided by the weight in mg added to the tube, or D E = Average W eight recovered (mg) W eight added (mg) The desorption efficiency is depen dent on the am ount of analyte collected on the charcoal. Plot the desorption efficiency versus weight of analyte found. This curve is used in Section 10.4 to correct for adsorption losses.

# Calibration and Standards
It is convenient to express concentration of standards in term s of mg/1.0 ml methanol. The density of the analyte is used to convert mg into m icro liters for easy m easu rem en t w ith a microliter syringe A series of standards, varying in concentration over the range of interest, is pre pared and analyzed under the same G C condi tions and during the same time period as the unknow n samples Curves are established by plotting concentration in mg/1 0 ml versus peak area N ote Since no internal standard is used in the method, standard solutions m ust be analyzed at the same tim e that the sample analysis is done. This will minimize the effect of known day-today variations and variations during the same day of the FID response.

# Calculations
Read the weight, in mg, correspond ing to each peak area from the standard curve. N o volume corrections are needed, because the standard curve is based on mg/1.0 ml m ethanol and the volume of sample injected is identical to the volume of the standards injected.

# D E P A R T M E N T O F H E A L T H , E D U C A T IO N , A N D W E L F A R E P U B L IC H E A L T H S E R V IC E C E N T E R F O R D I S E A S E C O N T R O L N A T I O N A L I N S T I T U T E F O R O C C U P A T I O N A L S A F E T Y A N D H E A L T H R O B E R T A T A F T L A B O R A T O R I E S 4 6 7 6 C O L U M B I