Overarching Issues

  1. Although many of the issues posed to the panel deal with approaches to past MP misapplications, the panel strongly recommends that efforts directed toward primary prevention (i.e., preventing future misapplications) be continued. In addition to the voluntary actions taken by the manufacturer and enforcement actions taken by the appropriate agencies, we recommend continued emphasis on health education to alert the public to the hazards of pesticide misapplications.
  2. Resources must be devoted to evaluating the effectiveness of alternative, cost-effective control strategies.
  3. More coherent planning is needed to effectively respond to these environmental health emergencies. Moreover, the planning for health education needs to be integrated with risk management.
  4. Members of affected households will be faced with difficult decisions regarding the risks of MP exposure and costs and benefits of alternative interventions. Risk communication and health education are critical to assist these people in making informed choices.
  5. The panel suggests that the steering committee explore the feasibility of using sentinel animal populations (e.g., household pets) as biomonitors for residential MP contamination.
  6. The panel has identified critical data gaps that must be urgently addressed so that scientifically based risk management decisions can be made. These gaps have been identified throughout this report but are again summarized here:

Field Survey of MP Environmental Degradation Products

The EPA should design and implement an environmental sampling study to determine the environmental degradation products of MP in indoor settings, especially PNP. The study should include a sufficient sample of representative homes (by region, time of application, type of application, etc.) to allow inference to other homes in the region.

7-day Study with Daily A.M. and P.M. Urinary PNP

The agencies should conduct a minimum 7-day pilot study of minimum daily a.m. and p.m. urinary PNPs in households currently undergoing environmental sampling. Individual environmental exposure questionnaires such be administered before each sample collection. In addition to urinary PNP, urinary creatinine should be measured on all samples to allow for creatinine adjustment. The study should be performed in a sufficient number of residences to make these observations under varying exposure conditions. The results of this study will help to determine the variability of spot urine samples, the usefulness of individual exposure questionnaire data in selecting optimal sampling times, and the value of adjustment for urinary creatinine.

NB: The public health protection of households participating in this more intensive monitoring overrides research issues: if on-site inspections demonstrate an imminent hazard situation or if urinary PNP results indicate overexposure in the course of data collection, the usual relocation interventions must be put into effect, regardless of the impact on the study.

Dermal Absorption Studies

Humans: The work group feels that it is critical to conduct a dermal absorption mass balance study correlating MP dermal dose with urine PNP excretion pattern in human volunteers. Such a study should be contracted to recognized experts in human dermal exposure studies and must be approved by the institution’s Institutional Review Board.

Animals: The effects of combined dermal exposures to MP and PNP, as well as combined exposure to MP and other pesticides identified in the field, should be investigated in a relevant animal model (pig, monkey, hairless guinea pig).

Subchronic Toxicity Study in Animals To Determine Dermal RfD

A subchronic toxicity study in rats to determine a dermal RfD for MP would be very useful for risk assessment in this situation. EPA and ATSDR should review available databases to determine if such data are currently available. If not, agencies should consider initiating such a study.

Pilot Study of Urinary PNP and RBC Cholinesterase

Data from occupationally exposed agricultural workers indicates that depression of RBC cholinesterase is unlikely at urinary PNP levels less than 1,000 g/L. The assumption that chronic low-level MP exposure will not depress RBC cholinesterase levels should be confirmed. A representative sample of people should be offered both urinary PNP and blood RBC cholinesterase monitoring. These may be individuals who are referred or self-referred to AOEC clinics for evaluation. If the sample is not random, sample should be compared with the target population in terms of levels of environmental exposure, urinary PNP, demographics, etc., to assess the possibility of selection bias. The RBC cholinesterase assays should ideally be performed by a single reference laboratory with demonstrated quality assurance for this assay. Before a single laboratory is identified, however, the issue of sample preservation needs to be addressed to determine if shipping samples to a central location is technically and logistically feasible.

Cohort Study of Neurobehavioral Effects in Children Exposed to MP in Utero and Postnatally

The panel recognizes the need for and importance of a cohort study to assess the relationship between in utero and postnatal exposure to MP and neurobehavioral effects in these populations. This epidemiologic study should be designed to address a key risk management question:

  • What is the dose-response relationship between indoor exposure to MP and neurobehavioral effects in the highest risk groups?

The study should be able to determine the exposure levels that produce no observable adverse effects on central nervous system function in these populations and would be very useful in setting future relocation criteria. This study is likely to be complex and expensive; nevertheless, it is a reasonable expenditure given the huge amount of resources devoted to current interventions. ATSDR should enlist the assistance of an expert peer review committee to assist in reviewing and providing guidance in the design of this study. There is a small window of opportunity to implement this study, especially if reversible effects are considered an important outcome.

Page last reviewed: June 20, 2014