Page 1

NOMINATING PARTY: The United States of America

DATE: MARCH 27, 2013

FILE NAME: USA CUE15 HAM FACILITIES

BRIEF DESCRIPTIVE TITLE: U.S. Response to MBTOC February 14, 2013 Questions on 

Ham Facilities 

SITE NAME (OPEN FIELD): Dry Cured Meat Products

NOMINATING PARTY CONTACT DETAILS:

Contact Person: Federico San Martini, Ph.D.

Title: Foreign Affairs Officer

Address: Office of Environmental Policy

U.S. Department of State

2201 C Street, N.W. Room 2657

Washington, D.C. 20520 U.S.A.

Telephone: (202) 647-3819

Fax: (202) 647-1052

E-mail: SanMartiniFM@state.gov

CONTACT OR EXPERT(S) FOR FURTHER TECHNICAL DETAILS:

Contact/Expert Person: Mark Hartman

Title: Acting Director

Address: Biological and Economic Analysis Division

Office of Pesticide Programs

U.S. Environmental Protection Agency

1200 Pennsylvania Avenue, N.W. Mailcode 7503P

Washington, D.C. 20460 U.S.A.

Telephone: (703) 308-0734

Fax: (703) 308-7042

E-mail: Hartman.Mark@epa.gov

BACKGROUND

The United States government nomination is for 3,240 kilograms of methyl bromide to fumigate 

aged country hams in 27 facilities. The pest of concern is Tyrophagus putrescentiae, the ham 

mite (also called cheese mite and mold mite), which infests the aging hams and renders them 

unsalable in the United States. No alternatives have been identified to control this pest under 

U.S. conditions. 

MBTOC Question 1. This CUN is completely silent on MBTOC’s most pressing need for 

information: why do some facilities fumigate 5x/yr when other facilities fumigate 2x/yr? This 

was the key concern of MBTOC last year when our recommendation was that each facility 
Page 2

improve gastightness, IPM, and take other measures to reduce frequency of fumigation by one 

fumigation per year (except those which already fumigate only twice per year.)

U.S. Reply

The frequency of fumigation is based on the biology of the pests, in this case primarily 

mites, Tyrophagus putrescentiae. If a processor visually sees mites, or signs of mites, on 

his hams and ham racks, he will schedule a fumigation with methyl bromide within 2 

weeks to make sure that the mites do not cause damage to the hams. The processors do not 

fumigate except when they need to reduce pest infestations. According to U.S. federal 

regulations, hams sold in the United States must be free of mites (21 U.S.Code 601(m)(3), 

9 Code of Federal Regulations 416.2(a)).

A thorough understanding of the biology of this pest, especially in relation to the 

environment, is under investigation by Dr. Phillips, but not completely elucidated. 

However, like all biological systems, this is greatly affected by the environment, both 

biotic and abiotic. For instance, some locales have higher pest pressure than others, and 

some have higher rates of re-infestations than others. For instance, temperature and 

humidity clearly play a role, as does the fat and protein content of the food sources. 

However effects of other factors have yet to be described. One factor that appears to play a 

major influence is the age of the hams (see also the U.S. reply to question 3 below). 

The basic generation time of T. putrescentiae, under optimal conditions, is about 9.5 days 

(25°C and 85% RH). Under these optimal conditions, longevity of females ranges from 66 

to 99 days (Boczek, 1991). A female mite can lay up to 500 eggs (Boczek, 1991). 

Therefore, this arthropod has more than 36 overlapping generations per year in these 

country ham aging rooms. 

Aging hams have both high fat and protein content needed by T. putrescentiae. In addition 

country hams in the United States provide nearly optimal temperature and humidity (26 C, 

75% RH) for maximum reproduction and longevity of mites. Data, from Schilling (see 

Table 1 below), indicate that the longer hams are aged, the greater the likelihood for mite 

infestations. 

While there is research into IPM strategies for this industry, currently none have been 

identified to control mite populations. Sanitation is already being practiced at all facilities. 

Further understanding of the parameters of this biological system is critical to developing 

more strategies. 

MBTOC Question 2. The CUN page 11 Table 3, indicates that the US request for MB was 

based on the standard dose plus 10% for contingency. The CUN suggests that this was how 

MBTOC calculated its recommendation last year. But the US is missing a key element of this 

recommendation which was that – in the absence of any technically valid justification for a high 

frequency of fumigation – MBTOC recommended a reduction of one fumigation per year for all 

facilities (except those already only fumigating twice a year). We then added 10% for 

contingency in the total amount to take into consideration possible adverse weather issues etc. 

The 10% contingency was not to be considered an allowable additional dosage rate. 
Page 3

(Two pertinent excerpts of the 2012 MBTOC Final report text box on cured pork have been 

added as an appendix to this letter for ease of reference.)

MBTOC has used a standard MB dosage of 20g/m3 for all MB fumigations for all the years it 

has been reviewing MB use and making recommendations. That standard dosage has not 

changed and MBTOC has not seen any technical valid argument to change the standard dosage 

rate. 

We clearly need receive information from USG containing the technical justification for the wide 

differences in frequency of fumigation by facilities. 

U.S. Reply 

The United States recognizes the standard presumptions identified in the Handbook on

Critical Use Nominations for Methyl Bromide, including the dosage rate of 20 g/m3for 

structural fumigations, and agrees with MBTOC’s 10% contingency for extenuating 

circumstances, such as adverse weather issues. However, we disagree with MBTOC for 

arbitrarily limiting the number of fumigations. 

The number of fumigations is dictated by the presence of mites on hams within the facility. 

As described above (Q1), the environmental conditions of the aging rooms are optimal for 

mite development. The hams themselves are an optimal source of protein and fat for 

maximum longevity and reproduction. And researchers have observed that the longer hams 

are aged, the more often they need to be fumigated to meet the U.S. regulations for 

unadulterated food products (see table below Q3). Since there are no technically and 

economically feasible alternatives, the industry needs to fumigate for mites when populations 

are observed. The costs of conducting the fumigation itself as well as associated 

inconvenience and lost time for the facility are a strong disincentive for fumigations to take 

place except when they are needed.

MBTOC Question 3. I note that during last year’s OEWG meeting, USDA’s Dr. Ann Bartuska 

gave me a table which correlates frequency of fumigation to length of storage time of the cured 

pork. I am concerned, however, that this was not given to us officially. If the US wishes to 

provide that table (and explain the data source of the information), and/or similar information, to 

us it might be a significant contribution to our understanding. It is certainly one of the pieces of 

information that we could use.

MBTOC is mindful of two facts: one is that our recommendation was not accepted by Parties last 

year and the second is that Parties demand that we do a diligent and technically correct 

evaluation of a requested use of methyl bromide. We can only do so if Parties provide needed 

information. Therefore we ask US to correct the oversight of this needed information in its 

CUN. 

Questions concerning volume of facilities fumigated:

U.S. Reply

The United States appreciates MBTOC’s follow-up question on the graph presented 

informally in November, 2012. Attached is Figure 1, “Number of fumigations per year based 
Page 4

on age of dry cured hams that are produced by various dry‐cured pork plants in the 

Southeastern United States.” This is the figure provided by Dr. Bartuska to a member of 

MBTOC last year. The information in the figure is the result of industry feedback in 2008 to 

a request for information from Dr. Wes Schilling of Mississippi State University. 

Because the figure may be difficult to interpret, we are also providing the data used to 

generate the figure. Table 1 shows the direct relationship between months of aging for drycured hams to the number of fumigations to address ham mite infestations. This data clearly 

shows that the longer a ham undergoes curing in storage, the more frequently fumigations 

with methyl bromide are required. Hams aged less than three months do not require any 

fumigation. Increasing the aging time to three months results in a majority (87%) of the 

hams requiring a single fumigation. In contrast, hams aged more than 6 months can require 5 

to 6 fumigations. Fumigations are ordered only when mite outbreaks are observed on ham 

racks and the hams themselves.

Table 1. Number of fumigations compared to age of hams, percent of total 

Maximum 

Number of 

Fumigations 

per Year

Age of Hams (months)

< 3 3 4 5 to 6 6 to 12 18 to 24

0 100 % 14 % 0 0 0 0

1 0 87 % 33 % 0 0 0

2 0 0 33 % 0 17% 0

3 0 0 33 % 100 % 0 0

4 0 0 0 0 50 % 0

5 0 0 0 0 0 0

6 0 0 0 0 33 % 100 %

Based on 27 facilities. Information collected by Dr. W Schilling, 2008.

The United States would like to note that this information is consistent with previous 

research. Rentfrow et al. (2006) found that aging times of longer than 5 months causes an 

increased risk for infestation with mites and beetles. However, aging for shorter times than 5 

months does not assure processors that infestation problems will not occur, and long aging 

times (> 6 months) are often necessary to obtain desired flavour and product quality that 

meets niche markets.

MBTOC Question 4. In May 2012, MBTOC asked the US to supply the following information: 

a total true volume of the aging rooms which are fumigated in each facility, irrespective of the 

number of fumigations. In other words, if one of the applicants’ aging rooms is fumigated 3x/yr 

we did not want them to multiply the volume of their aging room 3x and then report that as the 

volume. We then noted that we needed to know the average of how often each aging room is 

fumigated annually by each applicant.

U.S. Reply

In August 2012 the United States provided, on a per facility basis, the maximum methyl 

bromide used, aging room size, and the maximum number of fumigations per year. This 
Page 5

information was also included in the U.S. critical use nomination submitted on January 24, 

2013 (see table 3 of the U.S. critical use nomination). 

While each facility may be composed of multiple aging rooms, typically all the rooms get 

outbreaks of mites at about the same time. Aging rooms may be composed of wood, 

concrete, or cinder blocks with connections, such as electrical conduits and underground 

pipes and drains. While mites may be introduced into rooms when the doors are opened or 

closed, or on workers clothing, the openings between the aging rooms also allow mites to 

infest the neighboring rooms. When mites are observed in one aging room it is not long 

before they are found in other nearby aging rooms; therefore a fumigation will involve the 

entire aging room complex, or facility. 

While the table (Table 3 of the USCUN) listed separate facilities, each row represented the 

rooms that are fumigated together. Producers often have multiple small aging rooms in 

facilities separate from the offices. As a practical matter, all aging rooms are fumigated 

simultaneously as mite infestation in one room inevitably leads to infestations in adjoining 

aging rooms since ham mites, like dust mites, can be carried in air currents. In fact, 

professional applicators will often tarp (or tent or wrap) the entire building for a fumigation. 

Regarding the number of times an aging room might be fumigated, again please refer to 

Table 1.

MBTOC Question 5. Although the US then supplied information about the number of 

fumigations at each company, the requested information about the volume of the aging rooms 

and the number of times each aging room is fumigated has not yet been supplied. This 

information is needed to determine the correct amount of MB needed. 

U.S. Reply

All aging rooms within a facility are fumigated simultaneously (See reply to Q4).

MBTOC Question 6. The CUN pages 7-8 indicates the planned research on MB alternatives for 

cured pork. However, we believe the CUN was written several months ago. Could the US please 

confirm if this research has indeed started and if there have been any additions or deletions to the 

program of planned research? 

U.S. Reply

The CUN research update was written 2012 and is still current with one update regarding the

testing of mesh screens. 

Schilling and Phillips added research areas which include: Effect of temperatures between 

20° C and 40° C on mite growth on ham cubes; Development of food grade gels to cover the 

surfaces of ham and inhibit infestations; and evaluation of mesh coating and barrier bags for 

their potential to prevent mite infestations. 

Dr. Phillips writes: 
Page 6

“We will test the efficacy of 30 m (micrometer) mesh nylon for preventing mite 

infestation of ham pieces. We already have good results on "food-safe" coatings 

and dips, but these will need field validation.” 

MBTOC Question 7. Additionally, in its text boxes and previous correspondence, MBTOC 

suggested incorporating fine, mite-proof gauze into the system of preparing and storing cured 

pork. This suggestion does not seem to have been taken into account by the Party and is not 

mentioned in the CUN. Could the USG explain its views, and the intentions of its researchers 

and cured pork facilities, towards this technical recommendation? 

U.S. Reply

Dr. Phillips reports: 

“We will test the efficacy of 30 m (micrometer) mesh nylon for preventing mite 

infestation of ham pieces. We already have good results on "food-safe" coatings 

and dips, but these will need field validation.” 

Questions on phase out of MB for cured pork in the US:

MBTOC Question 8. Noting that European producers of similar cured pork products do not use 

methyl bromide for pest control, and noting the continuing use of MB in the US, MBTOC asks 

how the Party intends to phase out MB in this sector. 

U.S. Reply 

Researchers in the United States have conducted research on methyl bromide alternatives for 

many years and we continue to have a robust research program. Currently there are no 

technically and economically feasible alternatives for control of pests on U.S. dry-cured pork 

products. We hope that in the future alternatives will be developed that are technically and 

economically feasible for use in this sector. 

References: 

Boczek, J. 1991. Mite pests in stored food. In: JR Gorham, ed. Ecology, Management of FoodIndustry Pests. FDA Technical Bulletin 4. Association of Official Analytical Chemists, 

Arlington, VA. Pp 57-79. 

Rentfrow, G., Hanson,D.J., Schilling, M.W., Mikel, W.B. (2006) Methyl bromide use to combat 

mite infestation in dry-cured ham during production. 

http://mbao.org/2006/06Proceedings/108SchillingMMethylbromideusetocombatmiteinfestationin

%20dry.pdf.