Assessing levels of contaminants in breast milk: methodological issues and a framework for future research

Abstract

To assess the scale of the possible exposure by the breast-fed infant to potentially harmful substances in breast milk, methodologically robust studies are essential. Many studies in this field, however, do not report details of crucial issues such as recruitment and milk sampling. The aims of the study reported here were to develop robust methods for the study of contaminants in breast milk, and to develop a framework for future research and population monitoring. Three cohorts of women and babies were recruited by midwives from five sites in northern England. Cohort 1 (cross-sectional, n = 322) were asked to provide two milk samples, one at one week following birth and one at a subsequent time point. Cohort 2 (longitudinal, n = 54) were asked to provide five samples at specified time points over the first 12-16 weeks after birth. Cohort 3 (convenience, n = 18), mothers of babies in the Special Care Unit, were asked to donate surplus breast milk. A novel method of analysing fat concentration in small volumes was developed and tested. A randomly selected set of samples from different donors and stages of lactation was screened for organochlorine pesticide residues, polychlorinated biphenyls, dioxins/furans, phthalates and heavy metals. A total of 453 samples were donated. Cohort 3 was the least successful route of recruitment. Cohorts 1 and 2 combined were most representative of the population. Sample collection, transport and storage procedures, and the collection of data on life style and diet, were robust and acceptable to women. Midwifery involvement in recruitment was an essential component. This study offers a framework both for the conduct of future research studies, and for the establishment of regional and national monitoring mechanisms for contaminants in breast milk. Similar work on contaminants in formula as fed to babies is needed to inform risk assessment methods.

The Molecular Epidemiology of Chronic Aflatoxin Driven Impaired Child Growth

“…Some of the above studies have used this measure in attempts to better define maternal exposure whilst others are used to indicate risk of infant exposures. For lipophilic xenobiotics in general, the measuring and understanding of the kinetics and variations of those kinetics of the transfer from maternal exposure to breast milk samples are complex [70]. For aflatoxins a small survey from Gambia ( n = 5) over several days collection suggested that about 0.1–0.4% of the ingested AFB1 was transferred to milk [69].…”

An account of significant events influencing Australian breastfeeding practice over the last 40 years

“…(6) Avoid breast manipulation, nipple redirection and rapid thrusting of the baby to the breast. (7) Increase research and improve knowledge about the possible effects of pharmaceutical and other substances transported to the unborn and breastfed baby 95 and, (8) avoid overt and covert use and promotion of non-human milk products for babies.…”

Choosing the types of biological sample to collect in longitudinal birth cohort studies

“…caffeine, nicotine, alcohol), and illegal drugs, can also all appear in maternal milk (). Measurement of these substances or their metabolites in breast milk is tempting, and considerable effort has recently been devoted to demonstrating the feasibility of collecting and storing samples in a general population 50 . One of the problems is that the composition of milk varies throughout a feed, with a far higher concentration of fat at the start compared with the end of a breast feed.…”

“…Another problem concerns the fact that some substances (such as phthalates) degrade rapidly, and storage even at −70°C will not prevent this. In the short term, however, biodegradation seems not to be such a problem and samples can even be sent through the post satisfactorily 50 …”