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UNITED STATES ENVIRONMENTAL PROTECTION AGENCY

WASHINGTON, DC 20460

OFFICE OF CHEMICAL SAFETY AND POLLUTION PREVENTION

June 29, 2011

MEMORANDUM:

Subject: Occupational Exposure Assessment for the Proposed Use of Ammonium Sulfate 

as Nalco 60620 in Pulp and Paper Mill Water Systems 

PC Code: 005601 DP Barcode: D391275

Decision No.: 443828 Registration No.: 1706-EUN 

Petition No.: NA Regulatory Action: Product Registration – Section 3 

Risk Assess Type: Single Chemical Case No.: NA

TXR No.: NA CAS No.: 7783-20-2

MRID No.: 48340810, 48461201 40 CFR: NA

To: Tracy Lantz, Product Manager, Team 33

Regulatory Management Branch I

Antimicrobials Division (7510P)

From: Timothy C. Dole, CIH, Industrial Hygienist

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

Thru: Timothy Leighton, Senior Scientist

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)

And

Nader Elkassabany, Branch Chief

Risk Assessment and Science Support Branch (RASSB)

Antimicrobials Division (7510P)
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Introduction

The purpose of this memo is to evaluate the potential for occupational exposure and risk 

resulting from the proposed use of ammonium sulfate to treat pulp and paper mill water systems. 

This evaluation is based on the proposed label, an exposure evaluation submitted by Nalco, air 

sample results provided by Nalco and information from the literature.

Use Information

Nalco 60620 is proposed for the control of microbial contamination in pulp and paper mill 

water systems. It contains 20 percent ammonium sulfate as the active ingredient and it is used in 

conjunction with sodium hypochlorite (typically 12.5%) in a proprietary delivery system 

(OxiPro) to produce monochloramine on site. The OxiPro delivery system controller ensures the 

automatic production of the dilute chloramine solution, controls the optimization of the 

production process, and ensures the adequate dosing into the water requiring treatment. The 

treatment can be administered using the slug, intermediate or continuous feed methods. The 

specified dose is 1 to 10 ppm available chlorine for both initial and subsequent treatments. 

Exposure Assessment

As discussed in MRID 483408-10 “Nalco 60620 - Discussion of Applicator Exposure Data 

Requirement”, the OxiPro feed system is a closed system. The chemicals are supplied in 

refillable portable totes, semi-bulk containers, or from tanker trucks and are transferred through 

hoses to storage tanks. The chemicals are then transferred from the storage tanks into the 

OxiPro feed system and then the mixture is pumped into the mill process. Based on this 

information it is anticipated that exposures to the precursor chemicals ammonium sulfate and 

sodium hypochlorite would be minimal and would not trigger any risk concerns. Although not 

specifically stated on the label, it is anticipated that the reaction will be controlled by maintaining 

alkaline pH to enhance the production of monochloramine, which is only slightly volatile from 

water while minimizing the production of trichloramine (also called nitrogen trichloride), which 

is highly volatile. As discussed in Kovacic et al., 1970, the product of the reaction of ammonia 

with chlorine or hypochlorous acid is chloramine when the pH >8.

Air Sampling Data for Nitrogen Trichloride (NCl3

Nalco has submitted air sampling data (MRID 484612-01) where NCl3 air concentrations as 

total chloramines were measured in one paper mill that was using Nalco 60620 as a biocide (Mill 

#1) and in another paper mill that was using ammonium bromide as a biocide (Mill #2). 

Additional information regarding the characteristics of each mill was also reported in a letter 

(Mann, 2011b) from the registrant’s representative and is included in Table 1. It should be noted 

that the location and production rate of each mill was reported but is not included in Table 1 

because it is confidential business information.

) in Paper Mills
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Table 1 – Characteristics of Paper Mills Sampled in MRID 484612-01

Characteristic Mill #1 Mill #2

Location Confidential Confidential

Type of Paper 

Produced

Light weight coated 

Coated free sheet 

Uncoated free sheet 

Coated free sheet

Production Rate Confidential Confidential

Ventilation 

Design

Roof exhaust fans. Moisture capture 

from exhaust fans in the dryer section.

Roof exhaust fan. Pocket ventilators in 

the dryer section for moisture control.

Building 

Volume

12,000,000 cubic feet 6,000,000 cubic feet

Airflow Not Reported 580, 000 CFM (5.8 ACH)

The samples were collected by either an IH Consultant (Mill #1) or by a Nalco Industrial 

Hygienist (Mill #2) using a sampling method based on Hery, 1995. This method includes a 

sampling cassette that contains a PTFE pre-filter to trap aerosols containing nonvolatile amines, 

such as monochloramine, and chloride compounds followed by primary and backup quartz fiber 

filters impregnated with sodium carbonate and diarsenic trioxide to trap NCl3. Samples were 

collected at a flow rate of 1.0 liter per minute for 128 to 177 minutes at Mill #1 and for 240 

minutes at Mill #2. The samples were analyzed by Galson Laboratories, which is accredited by 

the American Industrial Hygiene Association, using ion chromatography in accordance with an 

in-house method based on Hery,1995. This method detects total chloramines and has a limit of 

detection of 6 ug per filter. 

The results of the air sampling are summarized in Table 1. These results indicate that for 

Mill #1, NCl3 air concentrations exceeded 0.011 or 0.14 mg/m3 for samples 2AR, 2ARB and 

2ARC while for the remaining samples, NCl3 did not exceed the limit of detection that ranged 

from 0.03 to 0.05 mg/m3

. The actual air concentration for samples 2AR, 2ARB and 2ARC is 

unknown because significant breakthrough was detected on the backup treated filter. In Mill #2,

the results ranged from non-detect to 0.13 mg/m3 and no breakthrough occurred though it was 

noted that heavy misting occurred at Location #1 and significant eye irritation was experienced 

at Location #2.
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Table 1 –Nitrogen Trichloride Air Sample Data Submitted by Nalco

Mill

(Date)

Location Sample 

ID

Duration 

(Minutes)

Result 

(mg/m3)

Treatment

Mill #1

(10/14/08)

Paper Machine – location confidential 2AR 135 >0.14* Nalco 60620

(Ammonium

Sulfate)

Paper Machine – location confidential 2ARB 153 >0.11*

Paper Machine – location confidential 2ARC 152 >0.14*

Paper Machine – location confidential 2CRFA 148 <0.04

Paper Machine – location confidential 2CRFB 177 <0.03

Paper Machine – location confidential 2CRFC 136 <0.04

Paper Machine – location confidential 2SPOFA 134 <0.04

Paper Machine – location confidential 2SPOFB 160 <0.04

Paper Machine – location confidential 4RSA 127 <0.05

Paper Machine – location confidential 4RSB 151 <0.04

Paper Machine – location confidential 4TRSA 128 <0.05

Paper Machine – location confidential 4TRSA 150 <0.04

Mill #2

(08/26/09)

Location #1 – Wet End Paper Machine –

Upper Platform Fourdrinier

082609-1 240 0.067 Ammonium 

Bromide

Location #2 – Basement Machine Room –

Platform Adjacent to Open Mix Chest

082609-2 240 0.13

Location #3 – Walkway Wet Machine Room –

Adjacent to Lab

082609-3 240 <0.02

*Break through occurred and the actual result could be greater than indicated. In addition, it is not known if these 

results reflect NCl3 or other chlorine species because a silica gel tube was not used.

The sampling method used by Galson Laboratories is based on the method developed by 

Hery, 1995 for use in evaluating NCl3 exposures in swimming pools. This method was 

subsequently modified in Hery, 1998 for use in food processing plants to include a sulfamic acid 

treated silica gel tube in front of the treated filters. This tube was added to capture other chlorine 

species such as hypochlorites, monochloramine and dichloramine which would make the 

method more specific for nitrogen trichloride (i.e. trichloramine). Since this tube was not used in 

the samples submitted by Nalco, the results are not specific for nitrogen trichloride and could 

instead reflect the presence of other chlorine species such as monochloramine. 

Conclusion

The registration of ammonium sulfate as Nalco 60620 is not anticipated to result in any risks 

of occupational exposure to ammonium sulfate because ammonium sulfate is of low toxicity and 

it is handled in a closed system. It is also anticipated that the reaction of ammonium sulfate with 

sodium hypochlorite will be controlled to enhance the production of monochloramine while 

minimizing the production of trichloramine. It is recommended that the conditions needed to 

prevent the production of trichloramine be stated on the label.

The samples submitted by Nalco indicate that chloramines, which could include nitrogen 

trichloride, were detected at air concentrations ranging from 0.067 mg/m3 to greater than >0.14 

mg/m3. The exact air concentration could not be determined, however, because breakthrough 

occurred. The identity of these chloramines is also unknown because the sampling method did 

not include a silica gel tube which would have screened out the less volatile amines such as 

monochloramine and dichloramine. 
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Human Studies Considerations

The exposure studies included in this risk assessment (Hery et al., 1995, Hery et al., 1998) 

have been cleared for use in risk assessment by the OPP ethics reviewers. 

References:

Kovacic et al., 1970. Chemistry of N-Bromoamines and N-Chloroamines, Kovacic, P., Lowery, 

M., Field, K., Chemical Reviews, Volume 70, Number 6, pp 639-665, 1970

Hery et al., 1995. Exposure to Chloramines in the Atmosphere of Indoor Swimming Pools, Annals of 

Occupational Hygiene, Volume 39, Number 4, pp 427-439, 1995.

Hery et al., 1998. Exposure to Chloramines in a Green Salad Processing Plant, Annals of Occupational 

Hygiene, Volume 42, Number 7, pp 437-451, 1998.

Mann, 2001b. Response to your email of May 11, 2011. Letter from Julie Mann of Steptoe and Johnson 

to Tracy Lantz of the Antimicrobials Division. May 13, 2011.