The legal status of unpasteurized milk changed in eleven states during the 12 year period from to Six states where raw milk distribution was illegal legalized herdsharing Kentucky, Michigan, North Dakota, Ohio, Tennessee, and West Virginia , two states with farm-gate sales legalized retail sales South Carolina and Utah , one illegal state legalized pet food sales Maryland , one state with legal herdsharing then legalized farm-gate sales Illinois , and one illegal state first legalized herdsharing and then legalized farm-gate sales three years later Wyoming.
As the subset of data is small, outbreak-incident rates for these five states have been averaged over the four-year before and after periods, shown in Table 3. There was no change in absolute number of outbreaks 6 outbreaks in each 4 year period and a slight reduction in relative outbreak rates due to population growth during this time.
Outbreak incidence rates per million persons before and after legalization of unpasteurized fluid milk in five states for which there is at least four years of outbreak data prior to and after legalization.
Pasteurizing milk and dating it for sale reflects what public health program
Figure 4 shows the average annual outbreak incidence rate per million persons in the U. Significant variability is seen both over time and between categories of legalization, in part representing fluctuations due to the small absolute number of outbreaks per year within each category. While the Retail category shows the highest overall level of outbreaks, there has been a clear downward trend since Similarly, the outbreak rate for Farm-gate states peaked in and has remained low since The highest variability is seen in the Herdshare and Illegal categories, potentially due to the lack of regulatory oversight in these states.
Outbreak incidence rate per million persons by legal status of unpasteurized milk, to excluding This summary of outbreak rates by legal status of the state Figure 4 masks variation between states within each category of legalization. Table 4 illustrates this variation by stratifying states according to average annual outbreak rate over the 12 year period. Within each of the four levels of frequency of outbreaks, there is wide variation on legal availability. Twelve states did not report any outbreaks from to , six of which provide legal access to unpasteurized milk.
While variability is necessarily expected due to the small absolute numbers of outbreaks reported per state, as above, these variations demonstrate that the legal status of unpasteurized milk is clearly not the only determinant of outbreak rate within a state. Variation also occurs over time within states. As an example, Vermont had the highest average annual outbreak rate at 0. Similarly, Washington State 0. States stratified by average annual outbreak incident rates for with excluded.
It is necessary to examine the relationship between outbreak rates and consumption trends in order to determine whether the decline in outbreak rates after may be due simply to a decline in consumption. However, this survey has not yet been repeated to allow a comparison, nor is there a national reporting system for unpasteurized milk production. It is therefore necessary to use other quantitative measures to estimate trends in consumer demand. One such proxy is the number of state-issued unpasteurized milk farm licences and permits. Annual totals for the number of licences and permits issued were requested from the fifteen state government agencies which license or issue permits to farms to produce and distribute unpasteurized fluid milk.
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Adequate data was received from nine of these agencies, representing a diverse geographic area and Missing licensing data were estimated by interpolating from confirmed numbers, as indicated by square brackets. Number of licences and permits issued to unpasteurized milk farms in nine U. Estimates indicated by square brackets. Legal status indicated by colour code as in Table 2. Assuming that licence and permit numbers are a reasonable proxy for consumption, and factoring in U. Estimated trend in outbreak rate controlling for population growth and estimated consumption rate, , scaled to show values relative to Census Bureau population estimates, and state government licensing information.
This calculation represents only an approximate indicator, as only nine states are represented, not all farms producing unpasteurized milk in each state might be licensed, not all licensing agencies maintain an ongoing record of the total number of current active licensees, and changes in farm-specific production levels are not reflected. As an example of how licence numbers may underestimate consumption rates, Missouri reports only one active unpasteurized milk licence while two consumer websites advertise 16 and 88 current sources of unpasteurized milk within that state, respectively , These examples suggest that our calculation may well underestimate consumption growth, such that the actual decline is likely to be more pronounced than what is shown in Figure 5.
The current study extends that analysis by expanding to cover a twelve year period from to , controlling for population growth, examining outbreak trends in jurisdictions in which legal status or availability of the product has changed, and estimating changes in consumption during the study period. In contrast with other studies 33 , , this paper does not include outbreaks caused by unpasteurized cheese.
Not only is unpasteurized cheese production and distribution regulated under Federal law and is thus unrelated to state-specific laws regulating unpasteurized fluid milk distribution, but processing itself introduces other factors which could affect relative risk, an issue which will be explored in a separate analysis. Also in contrast to other studies 34 , , this study excluded outbreak data from calculations due to data quality issues specific to that year Using data in longitudinal analyses of trends could therefore suggest a larger increase relative to that year than what actually may have occurred.
Given the four observed trends of a reversal in the number of reported outbreaks Figures 1 and 3 , increasing legalization Figures 2 and 3 , no increase in outbreak rates in five states which legalized raw milk Table 3 , and increasing consumption Table 5 , evidence was not found that supports the position that the legalization of unpasteurized milk within a jurisdiction will cause an increase in outbreaks.
Indeed, examining data up to and including shows that increased legal access after has been concurrent with generally declining outbreak rates, irrespective of change in consumption.
ᐅ Pasteurizing milk and dating it for sale reflects what public health program
As Figure 4 and Table 4 both illustrate, outbreaks can still occur in states where distribution is illegal, so legal prohibition itself is not a guarantee of consumer safety. A decline in outbreaks caused by a particular food vehicle could be due to reduced consumption of that food or to changes in methods of production, processing, and handling. As an example, the introduction of the HACCP hazard analysis and critical control points food safety system in meat processing plants throughout the U. Similarly, the decline in unpasteurized milk related outbreaks could be related to changes in product handling or to the implementation of bacterial testing standards and inspection programs.
Further studies should explore the efficacy of factors such as education and regulatory programs in preventing outbreaks, and in particular, examine what may have enabled some states e. Vermont and Washington to reduce outbreak rates to zero while others e. Utah have seen no decrease see Supplementary Table 4. Regarding education, a challenge for dairies has been a lack of on-farm food safety programs.
The decline in frequency of outbreaks coincides with the introduction of these targeted education programs. The tentative conclusion can be drawn that, similar to what was seen in the meat processing industry, the implementation of on-farm food safety systems for unpasteurized milk production may be related to the observed reduction in outbreak rates. Data from Pennsylvania supports this connection. As shown in Figure 6, outbreaks occurred each year from to , then no outbreaks were reported for or , then one outbreak occurred in In addition, in the proprietor of the largest Pennsylvania unpasteurized milk farm was trained and listed with the Raw Milk Institute While it is impossible to show causation, this correlation of fewer outbreaks with the implementation of a HACCP-based on-farm food safety training program has implications for further studies of the role which education and extension programs may play in the safe production and handling of unpasteurized milk.
Annual number of outbreaks and illnesses related to unpasteurized fluid milk reported in Pennsylvania, It should be noted that this study does not examine whether or not states which legalized raw milk also implemented mandatory licensing, bacterial testing standards, on-farm food safety plans, or farm inspections by state agriculture or health departments as part of the legalization process.
Regulatory programs such as these may well mitigate outbreak rates, and further studies should explore this question. For example, Vermont had three outbreaks between and , but has had no incidents since. This change coincides with an adjustment period after the introduction in of a stronger regulatory system The federal ban on interstate trade 57 in unpasteurized fluid milk has not eliminated either multi-state outbreaks or the emergence of unregulated interstate buying clubs.
As 43 states representing This study is subject to the limitations of the underlying data, as CDC does not have a record of all outbreaks which have taken place in the United States. Not all outbreaks are identified, investigated, or reported, and the source of foodborne illnesses are often not identified. Even when a single food is identified, the point of contamination is not always known or reported.
In addition, state bacterial standards were not examined in order to determine if these have an effect on outbreak rates, and it is recommended that this be the subject of a future study. A more significant limitation relates to the difficulty in estimating the actual extent of unpasteurized milk production or consumption. It is apparent from licensing statistics and consumer websites that unpasteurized milk is currently being produced on a larger scale than in past decades; however, with the lack of standardized reporting, and with many farms operating outside of any regulatory structure, any estimate of unpasteurized milk production necessarily incurs a large margin of error.
As the variability of state outbreak rates is not simply dependent on legal status, other factors beyond the scope of this study might be affecting the safety of unpasteurized milk production. Topics for further investigation could include: Together, such studies would provide valuable tools to aid in assessing the impact of policy decisions and state or federal unpasteurized milk regulatory structures, thus facilitating evidence-based decision making in public health. From a public health perspective, the lack of consistency and comprehensiveness in measuring production or consumption of unpasteurized milk is problematic; however, this analysis provides a current best estimate of the scale of disease outbreaks due to unpasteurized milk.
The potential for foodborne illness continues to be a small but real risk from consuming unpasteurized fluid milk, but analysis of data over a twelve year period demonstrates that increased access to this product within the United States has not led to increased outbreak rates. The evidence that legalization of unpasteurized milk has correlated with decreased outbreak rates has potential implications for public policy decisions.
Recent introduction of on-farm food safety training programs for unpasteurized milk producers may be a factor in the recent decline in outbreak rates. This in turn will enable the further development safe and minimally processed dairy products, to take advantage of the enormous public health benefits that would result from a significantly lower incidence of infections and allergic disorders provided by consumption of fresh, unprocessed milk. This study is based on publicly available data from the U. The legal status of unpasteurized milk was determined from National Association of State Departments of Agriculture NASDA unpasteurized milk surveys, state governments, and third-party websites.
Licensing data were obtained from state governments. Details of all dairy-associated outbreaks, as well as regulatory status and outbreak rate for each jurisdiction and year in the study period are available in the Supplementary Materials. All supplementary material is available at http: Funding Statement No funding was received for this study.
The authors have declared that no competing interests exist. Introduction Current information regarding the risks and benefits of unpasteurized raw dairy products is important for decisions regarding food safety policy, and is especially relevant given increasing demand for locally sourced, unprocessed foods, as well as in light of accumulating evidence for health benefits of consuming unpasteurized milk.
Methods Outbreak data collection and classification A foodborne disease outbreak is defined as an incident in which two or more people experience a similar illness resulting from the ingestion of a common food Data quality issues NORS data for was excluded from outbreak trend analyses due to data quality limitations specific to that year. State population scaling Annual population estimates from to were obtained from the U.
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- packaging, storage and distribution of processed milk.
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Legal availability of unpasteurized milk Information about state laws governing unpasteurized milk distribution was compiled from National Association of State Departments of Agriculture NASDA unpasteurized milk surveys for , , and 62 , 63 , 64 , state government websites 65 , 66 , 67 , 68 , 69 , 70 , 71 , 72 , 73 , 74 , 75 , 76 , 77 , 78 , 79 , and third-party sources 33 , 80 , 81 , 82 , 83 , 84 , 85 , 86 , 87 , 88 , 89 , 90 , 91 , This classification is noted because designation as pet food does not necessarily mean that the primary consumers are animals, as suggested by this Indiana Board of Animal Health statement: A systematic review and meta-analysis of the effects of pasteurization on milk vitamins, and evidence for raw milk consumption and other health-related outcomes.
Exposure to farming in early life and development of asthma and allergy: Clin Exp Allergy ; Farm residence and exposures and the risk of allergic diseases in New Zealand children. Farming exposure in childhood, exposure to markers of infections and the development of atopy in rural subjects. Which aspects of the farming lifestyle explain the inverse association with childhood allergy?
J Allergy Clin Immunol ; Consumption of unpasteurized milk and its effects on atopy and asthma in children and adult inhabitants in rural Poland. Inverse association of farm milk consumption with asthma and allergy in rural and suburban populations across Europe. Not all farming environments protect against the development of asthma and wheeze in children. A county milk commission which includes a physician and a veterinarian must first be established, committee regulations must be approved by the state, and milk can only be distributed within that county.
Only one county milk commission exists, and as of May no farm had received approval Virginia was classified as Herdshare H rather than Illegal I as the state permits them on a case-by-case basis 86 , with 67 listed on one consumer website Indiana was classified as Herdshare although it also has legal provision for pet food P , as this appears to be the more common distribution route: For simplicity, the year in which a jurisdiction changed status was assigned the new status.
Foodborne outbreaks may involve multiple states.
Pasteurizing milk and dating it for sale reflects what public health program
Numbers of active licensees and permit holders were requested from all state agencies which issue licences and permits to farms to allow them to produce and distribute unpasteurized fluid milk. Where data was not available from state governments, secondary sources such as conference proceedings and media reports were used 63 , 97 , 98 , 99 , , , , , , , , , , , , , , , , , Missing data were estimated by interpolating from confirmed numbers.
Over the twelve year period from January 1 to December 31 , there were 10, reported foodborne disease outbreaks, resulting in , illnesses, 10, hospitalizations, and deaths. Outbreak information for different food categories is displayed in Table 1. A caveat should therefore be made that this or any other comparative analysis which uses NORS outbreak data should be viewed in light of the fact that implicated foods remain undetermined in a large proportion of reported outbreaks.
Of outbreaks with identified food vehicles, 4. Of the dairy-related outbreaks, the pasteurization status of 17 could not be determined. Four of the unpasteurized dairy outbreaks involved both fluid milk and cheese products made from the same milk. Five of the outbreaks involved only goat milk and two involved both cow and goat milk. Table 1 also displays the average number of deaths per thousand illnesses. Unpasteurized fluid milk shows a similar figure 1.
Associated Data
Reported Foodborne Disease Outbreaks: Total Outbreaks and Dairy Categories from to Excluding data for 5 outbreaks , annual reported outbreaks related to unpasteurized fluid milk started at a low of 10 in both and and rose to peak at 18 in both and After this peak, outbreaks then saw a general decrease: This results in an annual average of 14 outbreaks for the most recent 5 year span, from to inclusive.
To analyze outbreak trends, it is necessary to control for changes in population size. When scaled using U. Census Bureau population estimates, outbreaks associated with unpasteurized fluid milk increased from 0. The value 0.