![](media/image1.wmf){width="6.0in" height="0.59375in"}UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, D.C. 20460

OFFICE OF

PREVENTION, PESTICIDES AND

TOXIC SUBSTANCES

April 4, 2006

**[MEMORANDUM]{.underline}**

SUBJECT: Sodium cyanide: Occupational Exposure Assessment and
Recommendations for the Tolerance Reassessment Eligibility Decision
(TRED) Document (RED Case 2560)

FROM: David Jaquith, Environmental Scientist

Reregistration Branch 4

Health Effects Division

THRU: Susan Hummel, Senior Scientist

> Reregistration Branch 4

#########  Health Effects Division 

TO: Rebecca Daiss, Risk Assessor

Reregistration Branch 4

Health Effects Division

Craig Doty, Chemical Review Manager

Special Review and Reregistration Division

DP Barcode(s): D318017

PC Code: 074002

MRID 46648901

###### 1.0 Background and Purpose

######  

The attached document addresses occupational exposures and risks for
sodium cyanide oxide to support the Health Effects Division (HED)
reregistration eligibility decision (RED) document. A RED was completed
in September 1994 (pre FQPA, ORE Chapter February 28, 1994) but the RED
did not consider the use for fumigation of citrus. A Phase IV review was
completed June 19, 1992 and did not consider the fumigant use.

###### 

2.  **Products and Formulations**

Sodium cyanide exists in two formulations; predator baits and for
fumigation of citrus shipped from California to Arizona. The application
rates are presented in Table 1. A more detailed summary of the labels is
presented in Appendix A.

*[Application Rates]{.underline}*

+---------------------+----------------------------+------------------+
| **Table 1: Sodium   |                            |                  |
| Cyanide Application |                            |                  |
| Rates**             |                            |                  |
+---------------------+----------------------------+------------------+
| Scenario            | Application Rate           | Fumigation Time  |
|                     |                            |                  |
|                     |                            | (hours)          |
+---------------------+----------------------------+------------------+
| Fumigation of       | 1 oz/100ft^3^ of Sodium    | 1 hour           |
| Citrus Fruit        | Cyanide (Equivalent to 6   |                  |
|                     | oz HCN/1000 ft^3^          |                  |
+---------------------+----------------------------+------------------+
| Animal              | 91.06 % sodium cyanide per | NA               |
| Baits/Injectors     | bait, up to 10-12 units    |                  |
|                     | per square mile            |                  |
+---------------------+----------------------------+------------------+

###### Fumigation Process

Sodium cyanide is registered in California as Special local need (SLN
CA-840006) for the generation HCN to fumigate citrus eliminate red scab
another surface pests prior to shipment to Arizona. It is used as
quarantine procedure to prevent the spread of these pests. Trailers are
fumigated with HCN using a closed system in which the appropriate amount
of sodium cyanide is mixed with concentrated sulfuric acid and water.
The trailers are fumigated for 1 hour. They are then aerated with more
than 10 air changes for ½ or 1 hour. The results of an air monitoring
are presented in Appendix B.

###### Bait Process

The use of sodium cyanide in bait products has been discussed in the RED
document in September 1994 and the ORE chapter for the review (W. Dang,
February 28, 1994) and will not be further considered in this report.

**3.0 Hazard Identification**

Cyanide is an acute toxicant. However, with the exception of citrus
fumigation the Agency has relied on incidence data to identify any
hazard associated with use of this compound. These data are compiled in
the following section.

**4.0 Incident Report**

Only 5 reports have been submitted by USDA APHIS concerning mishaps with
M-44 Capsules containing sodium cyanide since 1992 when EPA set up the
Incident Data System. None of the mishaps resulted in serious medical
outcomes. All resulted in transient symptoms which were minor to
moderate. Poison Control Centers have tracked rodenticide use of cyanide
over the years since 1985, however, their system does not specify the
form of the cyanide (e.g., calcium cyanide, sodium cyanide, or hydrogen
cyanide). On average Poison Control Centers receive only one report per
year. Most listed the outcome as not determined or, at most, minor
medical outcome. (Jerry Blondell, 2005)

**5.0 Non-Occupational/Residential Exposure**

. This material is not used in the residential environment

*[Label Requirements]{.underline}*

The end-use label for fumigation (EPA Reg. No. 39352-50001-AA) requires
the following regarding exposure and worker protection.

-   Where there is potential for dermal contact, full body personal
    protective equipment (PPE) must be worn. This includes solvent-proof
    gloves, clothing, hat, apron, and boots. Vapor-proof goggles are
    also required.

**6.1 Non-Cancer and Cancer Occupational Exposure and Risk Estimates**

**Short-/Intermediate-Term and Long-Term Inhalation Exposure**

There is potential for inhalation exposure to Sodium cyanide during
sterilization and post-sterilization activities; however current
exposure monitoring data are unavailable. A study was conducted. Rather
than collecting air samples and measuring HCN concentrations in an
analytical lab, a continuous monitor was used.

The current Occupational Safety and Health Administration (OSHA)
permissible exposure limit (PEL) for hydrogen cyanide is 10 ppm (11
milligrams per cubic meter (mg/m^3^)) as an 8-hour time-weighted average
(TWA) concentration. The OSHA PEL also bears a "Skin" notation, which
indicates that the cutaneous route of exposure (including mucus
membranes and eyes) contributes to overall exposure.

The National Institute for Occupational Safety and Health (NIOSH) has
established a recommend exposure limit (REL) for hydrogen cyanide of 4.7
ppm (5 mg/m^3^) as a STEL (Short term exposure limit, that level at
which an unprotected worker can be exposed for 15 minutes without harm).
NIOSH also assigns a "Skin" notation to hydrogen cyanide.

A NOAEL of 65 mg HCN/m^3^ based on mortality in 3 of 10 rats at the
LOAEL of 71 mg/m^3^ (HDT). Sprague-Dawley rats (15/sex/dose) were
exposed to acetone cyanohydrin (ACH)\[which is rapidly hydrolyzed to
hydrogen cyanide at physiological pH\] at concentrations of 0, 36, 101,
or 204 mg ACH/m3 for 6 hours/day, 5 days/week, for 14 weeks. Adjusted
for occupational inhalation exposure, the occupational is 50 mg/m^3^ (46
ppm). The exposures were equivalent to 0, 11, 32, and 65 mg HCN/m^3^.
The NOAEL reported from the study was 204 mg ACH/m3, corresponding to 65
mg HCN/m^3^. This can be estimated to correspond to a daily dose of 15
mg cyanide/kg BW/day. However, in a similar 4-week inhalation study at
an average ACH concentration of 211 mg/m^3^ (67 mg hydrogen
cyanide/m^3^), no systemic effects were observed, except on the first
day of exposure, when the concentrations in the chamber fluctuated and
reached values of 225 mg ACH/m3 (71 mg hydrogen cyanide/m^3^) at which
dose 3 out of 10 animals died. The dose-response relationship for
cyanide is thus very steep for inhalation exposure (Dykstra, 2006). The
NOAEL/LOAEL for the inhalation endpoint is based on the acute effect of
mortality for hydrogen cyanide. The MOE is based on the uncertainty
factor of 30X (3x interspecies factor and 10x intraspecies factor). The
traditional interspecies factor of 10X is reduced to 3X since the doses
are expressed as air concentrations and the pharmacokinetics is assumed
similar between animals and humans. The interspecies factor of 3x is
considered sufficient to account for only pharmacodynamic differences
between animals and humans.

While a NOAEL of 65 mg/m^3^ (60 ppm) has been established, this was
based on a continuous 6 hour exposure for 14 weeks. Adjusted for
occupational exposure, the inhalation exposure endpoint for hydrogen
cyanide is 50 mg/m^3^ (46 ppm). It is obvious from the study outlined in
Appendix B that any exposure in the workplace is transient in nature and
does not match the conduct of the toxicology study. The peak 15 minute
STEL from that study was 0.4 ppm (0.36 mg/m^3^). Using this value
results in a MOE of 115 even if is based on a very short term exposure.
It can reasonably be considered that the fumigation of citrus with NaCN
offers little in the area of risk.

####### Cancer Risk

There is no cancer concern for this chemical. No Q~1~^\*^ or MOE for
cancer has been established.

*[Short-/Intermediate-/Long-Term Dermal Exposure and Risk]{.underline}*

Since HCN is a gas used in outdoor environment, there is no dermal risk
from the gas itself. Potentially there could be a risk from the solid
salt. However incidence data does not support a quantified risk
assessment for dermal exposure

7.  **Risk Summary**

####### HCN is an acute toxicant. The very low level incidences indicate that risk from this chemical is minimal

**8.0 References**

1988 NIOSH PEL Project Documentation.
<http://www.cdc.gov/niosh/pel88/75-56.html>

American Conference of Governmental Industrial Hygienists. [TLVs and
BEIs Based on the Documentation of the Threshold Limit Values for
Chemical Substances and Physical Agents and Biological Exposure
Indices.]{.underline} Signature Publications. 2004.

EPA Reregistration Eligibility (RED) Sodium Cyanide EPA 738-R-94-020,
September 1994.

Memorandum from W. Dang (OREB/HED) to J. Smith (CCB/HED) titled
"Occupational and Residential Exposure Assessment and Recommendations
for the Reregistration Eligibility Document for Sodium Cyanide", dated
February 28, 1994.

Email from J. Blondell (CEB/HED), dated May 3, 2005.

  ---------------- ------------- --------------------------------------------
  **Appendix A.                  
  Summary of                     
  Labels For                     
  Sodium Cyanide                 
  Products.**                    

  **EPA Reg No.**  **Use**       **Comments**

  39352-50001-AA   Citrus        Ventilation to 5 ppm, HCN gas monitors
                   Fumigation    required, cloth or disposable garments and
                                 waterproof gloves are required, goggles or
                                 face shield required, two persons are
                                 required to be present, temperature not less
                                 than 60 degrees nor more than 80 degrees,
                                 restricted area of at least 20 feet around
                                 trailer, posting required, roll up doors are
                                 prohibited, 1 oz sodium cyanide per 100 ft³.

  35978-1          Predator Bait M-44 capsules, Certified Applicators only,
                                 posting required.

  56228-32         Predator Bait 

  39508-1          Predator Bait 

  56228-15         Predator Bait 

  1308-8           Predator Bait 

  39260-1          Predator Bait 

  35975-2          Predator Bait 
  ---------------- ------------- --------------------------------------------

## **Appendix B.**

## 

+--------+-------------------------------------------------------------+
| > **Ci | Krieger, R. (1999) \"Monitoring of Personal and Work Site   |
| tation | Air for Hydrogen Cyanide Resulting from Fumigation of       |
| >      | Citrus\": Final Draft Report. Project Number: HCN/3/99.     |
| Refere | Unpublished study prepared by University of California,     |
| nce:** | Riverside. 40 p. MRID 46648901                              |
+--------+-------------------------------------------------------------+

## 

## **INTRODUCTION**

Sodium cyanide is registered in California as Special local need (SLN
CA-840006) for the generation HCN to fumigate citrus eliminate red scab
another surface pests prior to shipment to Arizona. It is used as
quarantine procedure to prevent the spread of these pests. It is used to
fumigate sealed trailers, which are then aerated. These procedures are
described in more detail below.

**DESCRIPTION OF STUDY**

The study was conducted in February and March of 1999. Air
concentrations of cyanide were measured in the breathing zone of the
applicators and in the ambient air. The trailers were treated at a rate
of 1 ounce of sodium cyanide per 100 ft^3^ (\~ 6 ounces of HCN per 1000
ft^3^)

Trailers are fumigated with HCN using a closed system in which the
appropriate amount of sodium cyanide is mixed with concentrated sulfuric
acid and water. The trailers are fumigated for 1 hour. They are then
aerated with more than 10 air changes for ½ or 1 hour. In February one
trailer was fumigated 3 times and additional 5 trucks fumigated that
same day. In March one rig was fumigated prior to the start of
monitoring. This trailer was later fumigated and ventilated 4 more
times. In addition another trailer was fumigated and ventilated 3 times.
A total of 10 fumigation/ventilations were monitored during the study.
Each fumigation lasted for 1 hour.

Airborne HCN concentrations were measured using Safelog 100 datalogging
monitor. The monitors were zeroed using a compressed gas cylinder and
calibrated using a commercially prepared 10 ppm standard of HCN in
nitrogen. The flow rate was 400 mL per minute. One monitor was carried
in the breast pocket of the fumigator. One ambient monitor was located
50 feet from the trailer, somewhat farther than the 20 foot buffer zone
required by the label. Additional area monitors were located downwind at
distances of 50, 100, and 200 feet from the trailer. The high alarm for
HCN is 10 ppm. The high alarms for STE and TWA are each 4.7 ppm.

Following fumigation the trailers were ventilated for 1 hour through a
ventilation stack with a height of 20 feet 6 inches at a rate of 800
ft^3^/minute. Stack diameter was 3 inches.

The HCN levels of the personal monitor worn by the fumigator are
presented in Table B1. Exposure was low and no alarms were noted at any
time. Peak 1-minute levels were 4.7 and 5.6 for the two days. The peak
STEL was 0.4 for each of the days

+------------+--------+--------+--------+--------+--------+--------+
| **Table    |        |        |        |        |        |        |
| B1. Gas    |        |        |        |        |        |        |
| Detection  |        |        |        |        |        |        |
| Report for |        |        |        |        |        |        |
| the        |        |        |        |        |        |        |
| Fumigator  |        |        |        |        |        |        |
| (Monitor   |        |        |        |        |        |        |
| 1)**       |        |        |        |        |        |        |
+------------+--------+--------+--------+--------+--------+--------+
| Date       | Time   | Number | HCN    |        |        |        |
|            | Star   | of     | Levels |        |        |        |
|            | t-Stop | Tr     | (ppm)  |        |        |        |
|            |        | ailers |        |        |        |        |
+------------+--------+--------+--------+--------+--------+--------+
|            |        |        | Peak   | A      | Peak   | TWA^2^ |
|            |        |        | (1     | verage | S      |        |
|            |        |        | min)   |        | TEL^1^ |        |
|            |        |        |        |        | (15    |        |
|            |        |        |        |        | min)   |        |
+------------+--------+--------+--------+--------+--------+--------+
| Feb. 18,   | 10:27  | 3      | 4.7    | 0.0    | 0.4    | 0.0    |
| 1999       | am to  |        |        |        |        |        |
|            | 5:31   |        |        |        |        |        |
|            | PM     |        |        |        |        |        |
+------------+--------+--------+--------+--------+--------+--------+
| Mar.3,     | 9:00   | 7      | 5.6    | 0.0    | 0.4    | 0.0    |
| 1999       | am to  |        |        |        |        |        |
|            | 8:19   |        |        |        |        |        |
|            | PM     |        |        |        |        |        |
+------------+--------+--------+--------+--------+--------+--------+
| 1.  The    |        |        |        |        |        |        |
|     Short  |        |        |        |        |        |        |
|     Term   |        |        |        |        |        |        |
|            |        |        |        |        |        |        |
|   Exposure |        |        |        |        |        |        |
|     Limit  |        |        |        |        |        |        |
|     (STEL) |        |        |        |        |        |        |
|     to     |        |        |        |        |        |        |
|     which  |        |        |        |        |        |        |
|     an     |        |        |        |        |        |        |
|     u      |        |        |        |        |        |        |
| nprotected |        |        |        |        |        |        |
|     worker |        |        |        |        |        |        |
|     may be |        |        |        |        |        |        |
|            |        |        |        |        |        |        |
|   exposed. |        |        |        |        |        |        |
|            |        |        |        |        |        |        |
| 2.  The    |        |        |        |        |        |        |
|     tim    |        |        |        |        |        |        |
| e-weighted |        |        |        |        |        |        |
|            |        |        |        |        |        |        |
|    average |        |        |        |        |        |        |
|     (TWA)  |        |        |        |        |        |        |
|     is the |        |        |        |        |        |        |
|            |        |        |        |        |        |        |
|    average |        |        |        |        |        |        |
|     air    |        |        |        |        |        |        |
|     con    |        |        |        |        |        |        |
| centration |        |        |        |        |        |        |
|     taken  |        |        |        |        |        |        |
|     over   |        |        |        |        |        |        |
|     an     |        |        |        |        |        |        |
|            |        |        |        |        |        |        |
| eight-hour |        |        |        |        |        |        |
|            |        |        |        |        |        |        |
|    period. |        |        |        |        |        |        |
+------------+--------+--------+--------+--------+--------+--------+

The results of the ambient air monitoring are presented in Table B2. The
TWAs were all zero. The peak 15 minute STEL ranged from 0 to 0.6. The
latter was judged to be the result of displacement of a sunshade during
monitoring.

+---------+---------+---------+---------+---------+---------+---------+
| ##      |         |         |         |         |         |         |
| # Table |         |         |         |         |         |         |
|  B2. Am |         |         |         |         |         |         |
| bient A |         |         |         |         |         |         |
| ir Moni |         |         |         |         |         |         |
| toring  |         |         |         |         |         |         |
| Results |         |         |         |         |         |         |
+---------+---------+---------+---------+---------+---------+---------+
| **      | **      | **D     | **Peak  | **Av    | **Peak  | **TWA** |
| Monitor | Month** | istance | HCN     | erage** | STEL    |         |
| No.**   |         | from    | Level   |         | (15     |         |
|         |         | Trailer | (1      |         | min)**  |         |
|         |         | (ft)**  | min)**  |         |         |         |
+---------+---------+---------+---------+---------+---------+---------+
| 2       | F       | 50      | 2.3     | 0.0     | 0.0     | 0.0     |
|         | ebruary |         |         |         |         |         |
+---------+---------+---------+---------+---------+---------+---------+
| 3       | F       | 100     | 0.5     | 0.0     | 0.0     | 0.0     |
|         | ebruary |         |         |         |         |         |
+---------+---------+---------+---------+---------+---------+---------+
| 4       | F       | 200     | 0.3     | 0.0     | 0.0     | 0.0     |
|         | ebruary |         |         |         |         |         |
+---------+---------+---------+---------+---------+---------+---------+
| 5       | F       | 45      | 5.9     | 0.0     | 0.3     | 0.0     |
|         | ebruary |         |         |         |         |         |
+---------+---------+---------+---------+---------+---------+---------+
| 2       | March   | 50      | 2.2     | 0.0     | 0.0     | 0.0     |
+---------+---------+---------+---------+---------+---------+---------+
| 3       | March   | 100     | 1.2     | 0.0     | 0.0     | 0.0     |
+---------+---------+---------+---------+---------+---------+---------+
| 4       | March   | 200     | 0.9     | 0.0     | 0.6     | 0.0     |
+---------+---------+---------+---------+---------+---------+---------+
| 5       | March   | 45      | 1.0     | 0.0     | 0.1     | 0.0     |
+---------+---------+---------+---------+---------+---------+---------+